The antifertility effects of Carica papaya were investigated by feeding adult cycling and pregnant rats with different components of its fruits. No attempt was made to force-feed the animals. The results indicate that unripe fruits of papaya interrupt estrous cycle and induce abortions. The abortifacient property seems to decrease as the fruit becomes stale or ripe. Exogenous progesterone counteracts partially the adverse effects on pregnancy and the surviving foeti are without any distinct malformations.