The recently ruptured follicles of the avian ovaries were found to contain an oxytocic substance. The substance was found to be heat-labile, nondialyzable and not extractable by lipid solvents. The crude homogenate stimulated the frequency and amplitude of the chicken infundibulum, uterus and uterovaginal junction, if they were taken from hens 2 h before predicted oviposition. The homogenate was found to induce premature oviposition and to stimulate the uterine contractions of rats treated with progesterone. Uterine tissues taken from estrogen-treated rats either did not respond to the homogenate or were inhibited. Addition of phenoxybenzamine or propanolol did not inhibit the stimulatory effect of the homogenate. It is possible that this factor might be involved in regulating oviposition in the hen.