Lysine-vasopressin and oxytocin were tested on the normally neotenous adult Mexican axolotl, Ambystoma mexicanum, to determine their influence on metamorphosis. The salamanders were divided into four groups, and daily injections of saline, lysine-vasopressin, oxytocin, and TSH were made over a 28-day test period. Tail height, gill length, and body weight were measured as indicators of metamorphic change. Additionally, thyroid uptake of '"I was determined.The results showed that the vasopressin and oxytocin groups had a significant (P