The article presents some scientific results of the 6th Western Himalayan Interdisciplinary Biogeographical Expedition of the St. Petersburg Union of Scientists. The flora and vegetation types of the central part, north-east, east and south-east of Himachal Pradesh state (India) were studied. The expedition participants studied plants at altitudes from 200 to 4600 meters. The difficult terrain, the variety of combinations of rocks, soil types, as well as abrupt changes in meso- and microclimatic conditions significantly influenced the nature of vegetation and the composition of flora, the definition of phytocenotic boundaries, the search for rare plants and the clarification of their ecology. Attention was also paid to cultivated component in plant communities. The article, based on the professional interests and individual view of each of the authors, briefly represents the diversity of vegetation along a route of almost 2000 km, passing through all the vertical zonality of the Western Himalayan biogeographical province.