Abstract：This study was conducted to help clarify seasonal changes in fecal testosterone of wild Tibetan macaques (Macaca thibetana). The study was conducted over a 12-month period (October 2005 - September 2006)at the Huangshan National Park. The study period encompassed the 7-month mating season as well as the 5-month non-mating period. A total of 426 fecal samples from five wild,adult male Tibetan macaques were collected. Fecal testosterone was analyzed via radioimmunoassay (RIA)following standardized procedures. The results showed that testosterone levels varied significantly across the 12 months in the Yulinkeng YA2 troop (P <0.01),and that the concentration of fecal testosterone during mating season [12.28 ± 5.75 ng/ ml (Mean ± SD)]was significantly greater (P < 0.01)than during non-mating season (9.42 ±4.99 ng/ ml). Testosterone levels were significantly different between mating season and non-mating season for all the five adult males (P <0.01). There also were positive correlations between fecal testosterone and environmental temperature (P< 0.05),and were highest or lowest in the early or later parts of the mating season,respectively. These results support earlier reports that wild Tibetan macaques display seasonal breeding. Further,seasonal variation in testosterone appears to be influenced by environmental temperature.