We monitored testicular and ovarian morphologies, seminiferous tubules, the sexual segments of the kidneys (SSK), follicular histologies, and male testosterone and female estradiol to define the reproductive pattern of Calotes emma and Calotes versicolor. Samples were collected monthly at Sakaerat Environmental Research Station in Thailand for 1 year. Testicular hypertrophies occurred at a time characteristic for each species, with their time course corresponding well to both active spermatogenesis and the hypertrophied SSK. Gravid females were also found at a time characteristic for each species. In active reproductive females, oviductal eggs were concomitantly encountered with ovarian vitellogenic follicles. The previtellogenic and vitellogenic follicles corresponded well to granulosa layer alterations. The distinct large pyriform cells were present in the granulosa layer of previtellogenic follicles but disappeared from the vitellogenic follicles. Male testosterone levels rose during testicular and SSK hypertrophies, and female estradiol levels increased during active reproductive stages of late vitellogenic follicles and gestation. We suggest that the reproductive patterns of C. emma and C. versicolor fall into the same reproductive pattern of annual continual reproduction, but that the time courses of such events are different in the 2 Calotes, and even in individuals of the same Calotes population.