The attrition of biodiversity is an issue of global concern. In ecosystems, building blocks are disappearing, one by one. The number of species, which are going threatened is increasing gradually (IUCN, 2003). The numbers of threatened plants are approximately 8457, out of which 247 plants are found in various biodiversity hotspots of India (IUCN, 2010).The use of plants by the inhabitants of the region for medicine, as edible, fodder, fuel, timber, in making agriculture tools, religious and various others have occurred since time immemorial (Samant and Dhar, 1997, Samant et al., 1998 b; Sarma et al., 2010).The resurgence of public attention in plant-based medicine connected with the quick expansion of pharmaceutical industries leading (prompting) to overexploitation that threatened many valuable medicinal plants (Kumari, 2011; Kumari et al., 2011, 2012). Further, the level of threat to natural population of medicinal plants has increased. There are more than 90% of the plant raw materials for herbal industries in India sourced from natural habitats (Tandon, 1996; Dhar et al., 2002). Singh in 2002 reported that 25% of all species could become extinct in coming 20 to 30 years. The fragmentation or loss of habitat by excessive (extreme) clearing of native vegetation possesses a significant threat to floristic and faunal diversity (Maron and Fitzsimons, 2007; Ford et al., 2009).The constant exploitation of various medicinal plant species from the wild (Kala, 2003) and substantial loss of their habitats during last 15 years have resulted in a population loss of various valuable medicinal plant species over the years (FAO, 2003). The major threats to medicinal plants are those that affect (influence) any type of biodiversity which are utilized by peoples (Rao et al., 2004; Sundriyal and Sharma, 1995). The debility of traditional laws, which have regulated the utilization of natural resources, is among the reasons for threatening the medicinal plant species (Ghimire et al., 2005; Kala, 2005).Belt and Kit in 2003 stated that these traditional laws have regularly proved to be simply damaged by modern socio-economic forces. Kala, 2002, 2005; Weekley et al., 2001 and Oostermeijer, et al., in 2003listed many potential reasons of rarity in medicinal plant species, such as climatic changes, explosion of human population, fragmentation and degradation of population, genetic drift, habitat alteration and specificity, heavy grazing, introduction of non-natives, land-use disturbances and narrow range of distribution.The insufficient available data on the threatened species in nature, however, has restricted their categorization to a few species on the basis of (based on) herbarium collection and by consultation by a couple of specialists (Kala, 2000). The present works are also questioned (addressed) for the validity on the task of threat categorization of the species. The problems in assessing the species diversity are increased in the Himalayan region, in respect of high altitude areas because of inhospitable climatic conditions, rough and detachment of the terrain and short life cycle of plants (Kala, 2006). For the collection of medicinal plants, indigenous communities and commercial herb gatherers also raid these same regions. Therefore, the predictable population density of categorized threatened medicinal plants is not exact because it varies the region that never and scarcely undergone any collection visits of such rare medicinal plant species (Kala, 2004).For long or short term management planning, an area-specific threat categorization of medicinal plant species is very important (Singh et al., 2009). The present study represents such an effort in the study area, using information on various attributes. The availability of vulnerable, endangered and critically endangered medicinal plants indicates high anthropogenic pressure on these plants. If habitat degradation and over-exploitation of these species continuously, they may disappear from the area within a few upcoming years (Singh et al., 2009; Kumari et al., 2012; Sharma et al., 2014).Population assessment of threatened species using different ecological methods and identification of key areas as medicinal plants conservation areas, i.e., MPCAs for in situ conservation, with the involvement of the local inhabitants and forest department of the area are recommended. Mass propagation using traditional (seed and vegetative) methods, for ex situ conservation. There is need of establishment and conservation of medicinal plants nurseries and herbal gardens and ensuring the availability of quality planting material for cultivation, including educational and awareness programmes for large-scale cultivation are recommended (Singh et al., 2009; Kumari, 2011; Kumari et al., 2011, 2012; Sharma et al., 2014).Using six attributes (i.e. habitat preference, distribution range, population size, use pattern, extraction trend, native and endemic species) the threat status was identified and also, categorization of these species is done as, Least Concern, Near Threatened, Rare, Vulnerable, Endangered and Critically Endangered following (Jain, 1991; Samant et al., 1998a; Dhar et al., 2002; Ved et al., 2003; Kala, 2006; Singh et al., 2009). Species with the combination of these criteria (S. No. 1, 2 and 3) were given marks accordingly. Species with scores 60 as critically endangered (Table-5.1).The present study deals with a threat analysis of threatened plants selected from our study site, such as Baliospermum montanum (Willd.) Muell.-Arg., Bergenia ciliata (Haworth) Sternb., Celastrus paniculatus Will., Clerodendrum serratum L., Coleus barbatus (Andr.) Benth, Costus speciosus (Koenig ex Retz.) Sm., Curculigo orchioides Gaertn., Dioscorea deltoidea Wall. ex Griseb., Drimia indica (Roxb.) Jessop., Gloriosa superba L.,Habenaria intermedia D. Don, Heracleum lanatum Michaux, Malaxis acuminata D. Don, Oroxylum indicum L., Pittosporum eriocarpum Royle.,Thalictrum foliolosum DC.,Valeriana hardwickii Wall.,Valeriana wallichii DC., and Zanthoxylum armatum DC. in different areas of Betalghat block of district Nainital in its natural habitats (Table 5.2).The present study records 21species of threatened plants belonging to 16 families and 18 genera. Out of which 2 species were trees, 4 shrubs and 13 herbs. The families were Caprifoliaceae, Lamiaceae and Orchidaceae, having two species and Apiaceae, Asparagaceae, Bignoniaceae, Celastraceae, Colchicaceae, Costaceae, Dioscoreaceae, Euphorbiaceae, Hypoxidaceae, Pittospraceae, Ranunculaceae, Rutaceae and Saxifragaceae having single species were identified. The distribution of threatened plants along an altitudinal gradient indicated maximum diversity in the zone 1001-1300 m and 1301-1600 m ( i.e. 15 spp.), followed by the zone 1601–1800 m (12 spp.) and 700-1000 m (11 spp.), respectively. Overlapping within different altitudinal zones is noted in most of the cases. Among all the habitats, moist forest habitat showed maximum diversity of threatened plants (i.e. 15 spp.), followed by exposed places (6 spp.), field margins (5 spp.) and agricultural fields (3 spp.). The richness of the species within the habitats is shown in figure (00). Out of21 threatened plants, 10 species having trade value and five species having self-use extraction. In the present study, 5 species were identified as native to the Himalayan region and 17 species as non-native. In the present study 2 species (Thalictrum foliolosum DC., Valeriana wallichii DC.) with scores 40-44 were considered as least concerned category, 8 species (Baliospermum montanum Will., Bergenia ciliata (Haworth) Sternb., Celastrus paniculatus Will., Clerodendrum serratum L., Costus speciosus (Koen.) Sm., Curculigo orchioides Gaertn, Dioscorea deltodea Wall., Valeriana hardwickii Wall) with score 48 were found under near threatened category and 5 species (Coleus barbatus (Andr.) Benth., Gloriosa superba L., Habenaria intermedeia D. Don, Malaxis acuminata D. Don and Oroxylum indicum L.) with score 52 were found under vulnerable category. The total percentage of near threatened (species) was (52.38%), vulnerable (species) (38.10%), and least concern (9.52%) (Fig 5.1). Based on the above criteria of threat categorization, obtained scores of threatened plants are presented in Table 5.3.The himalayan region has rich biological diversity that is now under threat from rapidly expanding human populations, habitat destruction and concomitant environmental degradation occurring at a fast pace. There are major gaps in our knowledge of biological resources and how biological diversity is maintained (Heywood, 1995).At the global, national and region levels attempts have been made to identify threatened species, including medicinal plants, using different attributes such as habitat preference, biogeographical range, population size and use pattern (Bryde, 1979; Jain and Sastry, 1980; Ayensu, 1981; Rabinowitz,1981; Beloussova and Demisseva, 1981; Pangtey and Samant, 1988; Samant et al., 1993, 1996; Sarvalingam and Rajendran, 2016; Sharma et al., 2017b; Singh et al., 2017). Observed status, IUCN status, and threat are to be seen in table 5.4 placed below. A total of 121 species of vascular plants including 17 species of medicinal plants from IHR have been recorded in the Red Data Book of Indian Plants (Nayar and Shastri, 1987, 1988, 1990). It is therefore evident from the present investigation that all the documented threatened plants of present study belong to different threat categories according to the Red Data Book of Indian Plants(Nayar and Sastry, 1987, 1988, 1990), field observations of the authors. At global and regional levels threat categorization have been also done in which Baliospermum montanum (Willd.) Muell.-Arg. and Celastrus paniculatus Will. have been recorded under the near-threatened category, Bergenia ciliata (Haworth) Sternb., Clerodendrum serratum L., Curculigo orchioides Gaertn, and Thalictrum foliolosum DC. under the vulnerable category, Gloriosa superba L. and endangered categories and Dioscorea deltoidea Wall. ex Griseb., Valeriana wallichii DC. under the critically rare categories (BCPP, 1997).