From 1985 to 1987, four new localities with abundant fossil mammals were dis-covered by Cao, Tian and others in the Zhoukoudian (Choukoutien) area, Beijing. They are theEast, West, Shangdian and Donglingzi caves. The East Cave fauna consists of 28 speices ofmammals and its age is middle Early Pleistocene. The East Cave assemblage shows that a tem-perature-falling event took place at around 1.20 Ma B.P. at Zhoukoudian. Sixteen species ofmammals were collected from the West Cave, which are mainly forms of late Early Pleistoceneage. The West Cave fauna represents a transitional fauna from the East Cave fauna (dry-cold)to the fauna (warm) at locality 9. The Shangdian Cave fauna is composed of four forms, beingMiddle Pleistocene in age. The Donglingzi Cave fauna contains 21 Late Pleistocene forms. Inthe cave two fossil horizons may be distinguished. The age of the lower horizon is early LatePleistocene, which is equivalent to that of the New Cave fauna; while the fauna of the upper ho-rizon may be correlated with the Upper Cave fauna.