Detailed reproductive data on this salamander endemic to Lake Patzcuaro, Michoacan, are reported for the first time, and were obtained from a laboratory colony. This species is relatively easy to culture in the laboratory, and it should be useful in experimental zoological studies. The courtship resembles closely that ofAmbystoma tigrinum.Four matings resulted in deposition of 9 to 16 spermatophores. The large (10 to 28 mm in diameter) spermatophores are topped by an undetachable cap of seminal fluid (2times3 mm). Females apparently removed some seminal fluid from each of several caps. About one day after courtship each female laid eggs, 290 to 1120 per female per spawning; the total complement per year is probably 300 to 1700 depending on the size of the female. The relatively small (2.0–2.2 mm vitellus) and lightly pigmented eggs were attached to the substrate in long strands, in single fil