In the present study the effect of petroleum ether extract of carrot seeds and progesterone on implantation have been investigated. 0·6 ml/100 g body weight of carrot seed extract was administered subcutaneously from days 1–7 of pregnancy and laparatomized on day 8. No implantation sites were observed. Thereafter graded doses of progesterone 2, 4 or 8 mg/100 g body weight was administered upto day 15 and autopsied on day 16. Two mg of progesterone did not show any effect. However, 4 mg of progesterone treated rats had smaller implantation sites compared to the controls whereas, 8 mg of progesterone was most effective with the result that in almost all the rats, delayed implantation was observed.