Previous studies have shown both prolonged and plastic cycles in viviparous females of the genus Liolaemus (Iguania: Liolaemidae) from the cold temperate climate of Patagonia. Males have shown interspecific variation in the duration of the breeding season, ranging from continuous to annual. Both cycles are far different from the reproductive cycles previously described for lizards from temperate climates. I examined maximum juvenile size, growth, sexual dimorphism, male and female reproductive cycles, and litter size of viviparous Phymaturus patagonica (Iguania: Liolaemidae), a species restricted to rock promontories in the Patagonian steppe. The reproductive cycle in males is annual with spermatogenesis beginning in December and peaking in early spring of the next year. Spermatozoa are stored in the epididymides for at least two months until mid-January. In contrast, females have a biennial cycle. Thus, prolonged female cycles and large interspecific differences in male cycles characterize viviparous lizards from Patagonia.