We studied perch height in a population of the arboreal lizard Anolis nebulosus from Chamela, Jalisco, México. A total of 1697 lizards were captured during 1988 (June through December), 1989, 1990, and 1991 (June through July). Males used higher perches than females, particularly during the reproductive season. At the beginning of the reproductive season (March) males started to use higher perches, which were highest during the peak of reproductive activity. However, perch height use by females did not follow the same pattern. Females used high perches in March before beginning reproduction, lower perches during the reproductive season from June to August and higher perches again in October at the end of reproductive activity. These patterns suggest that reproductive activity is an important factor determining differential perch height use between sexes, with the priority for males being courtship displays and defense of their territory, whereas protection from predators is more important for females. Adults used significantly higher perches than juveniles and hatchlings, and overall perches were significantly higher during the wet than during the dry season. Perch height of females and males increased with body, environmental, and microenvironmental temperatures, suggesting that perch height might play an important role in thermoregulation.