Dated charcoal and humic materials in soil, both which are evidence of forest fire and vegetation changes, as well as micro fossils such as pollen and opal phytolith (plant opal) in soil indicate occurrence of past deforestation in the Himalayan region. Timing and causes of the deforestation were discussed. Severe damage was inflicted between the late 10th and first half of the 20th century in Sirubari, central Nepal. Human impact such as population growth and cultural change due to the prosperity in the Kathmandu Valley and the active cultural exchanges between Nepal and India may have accelerated an environmental change during the 14-15th centuries. The deforestation during this period in central Nepal may have been caused by forest burning for shifting cultivation The evidence of deforestation in the Khumbu area was resulted from the immigration of Sherpas from Tibet in the middle of 16th centuries. Intensive outbreaks of fire during the period between the late 8th and 12th centuries have been reported in the Potechu valley, eastern part of the Nyainqentanglha Mountains, southeastern Tibet, as well as relatively intense fire in the Solu-Khumbu area. The earlier dates (the 8th century) of the deforestation of the period correspond to the timing of territorial and ethnic expansion of Tibet in the 7th to 9th centuries. In this period forest fire occurred frequently, but the results of pollen analysis at Phaplu in the Solu area indicate that nearly natural forest was maintained in a large part of the area at around the 9th or 10th century. This means that the forest could have recovered after the fire had ceased at least up to the late 10th century. Evidence of forest fire over the millennia was reported in Iunbesi and Namche, the Solu-Khumbu area and the Potechu valley, southeastern Tibet. Temporary deforestation caused by hunting and grazing is evident of having started at several thousand years ago. Human activities in the eastern Himalayas and southeastern Tibet may have extended perhaps nearly 10,000 years earlier. In conclusion, temporary hunting and grazing started several thousand years ago in the Himalayan area, but intensive agricultural land use and severe damage occurred between the late 10th and first half of the 20th century.