Oxytocin dosage was determined experimentally for the red-eared slider (Trachemys scripta elegans). Five dosages including 20, 10, 5, 4, and 2 units/kg were experimentally compared in 253 female turtles in a series of experiments conducted in 1999 and 2000. The 3 highest doses were equally effective overall following a maximum of 2 injections. The 2 lower doses were equally effective overall following a maximum of 2 injections. Success rate (i.e., turtles laid all eggs or retained 2 or fewer eggs following a maximum of 2 injections) ranged from 100% (20 and 10 unit/kg doses) to an average of 88.9% for the lowest doses (4 and 2 units/kg). When reduction in oxytocin exposure is desired, the lower dosages are recommended; when turtles are being treated for egg retention, the higher dosages may be more desirable. No difference in oxytocin efficacy was found among 3 species of chelonians (red-eared slider; stinkpot, Sternotherus odoratus; and painted turtle, Chrysemys picta) when oxytocin was given at 4 units/kg. No difference in efficacy was found among 2669 red-eared sliders from 2 collecting areas in west-central Illinois induced with 4 units/kg between 2000 and 2005.