This 1991–1992 study was designed to expand previous research on body weight (BW) in Tibetan macaques (Macaca thibetana) at Mt. Emei. Data on BW were collected in late autumn (LA) and late winter (LW) in groups ranging above 1,200 m. Over the winter, the BW fell significantly from a mean of 16.8 to 11.4 kg in females and from 19.5 to 17.0 kg in males. The previously reported BW means of 12.8 kg for females and 18.3 kg for males, measured in late spring, are near the center of the annual BW range for this species. In addition, with the sharper decline of female BW (−32% vs. −13% seen in males), the sexual dimorphism (M/F) in BW increased from 1.16 in LA to 1.49 in LW. This finding may be related to differential parental investment by two sexes. © 1994 Wiley-Liss, Inc.