From August 2001 to August 2002,a one-year study was carried out in the upper Zayu River basin,southeast Tibet,where systematic investigations on mammals were lack.The purpose of the study was to clarify the status of large and medium-sized mammals and factors threatening them.Twenty transects(10m) were set to survey the distribution,habitat and relative density of these mammals.Questionnaires were issued to get to know income and hunting activities of the villagers in the region.Mainly,21 species belonging to the orders of Primate,Carnivore and Artiodactyl were involved in this survey.Among these mammals,black muntjac was proved to be distributed in the study area for the first time.It was found that ungulates,especially takin and serow,were relatively abundant,while most species belonging to Carnivore Order were very rare,and even several of them has been probably extinct.Large and medium-sized mammals distributing locally were also major trophies of local hunters,which amounted to 82% of all families,and were important source of income and meat.Hunting was the most direct factor threatening these mammals,which caused fast declining of many animals,especially musk deer and Asiatic black bear.Besides hunting,human activity and habitat destruction also impaired the survival of these mammals.Based on these and previous studies,29 species of large and medium mammals in all are distributed in the region,28 of which belong to Class I or Ⅱ protected species in China.It was suggested that protecting these animals should be combined with promoting local economy.For conservation and development,six suggestions were put forward to resolve the local problems.