Female reproductive cycle and clutch size are important life history traits in lizards that can be influenced by biotic and/or abiotic factors. Here, the ovarian cycle and clutch size of a high-elevation population (15001600 m) of Aspidoscelis costata costata in Central Mexico are described. Females were collected monthly between 2005 and 2007, and their reproductive condition was evaluated based on appearance and size of ovarian follicles and presence/absence of oviductal eggs. The reproductive cycle was markedly seasonal with asynchrony in reproductive condition among females. Vitellogenic and gravid females were recorded from April (end of the dry season) through July (middle of the rainy season). Although this population inhabits a semi-humid warm climate, the timing of female reproduction in A. costata costata is similar to the cycle of temperate-zone species of Aspidoscelis . Females produced a single clutch annually with an average clutch size of 7.7 ± 0.44 eggs (median 8 eggs, range 414), which is the largest reported to date within the genus Aspidoscelis.