Objective: To evaluate the preliminary antiimplantation activity of isolated pure principles from successive extracts of petroleum-ether (PE) and ethyl acetate (EAc) and subsequent crude alcoholic extract of seeds of T. populnea in female albino rats. Material and Methods: Graded doses of the active principles and the crude alcoholic extract (in 1% gum acacia suspension) were tested for possible antiimplantation activity in Sprague-Dawley female rats of normal estrus cycle after overnight cohabitation with males of proven fertility. The day when spermatozoa was detected in vaginal smear was treated as 1st day of pregnancy. The compounds were administered to female rats from the 1st day to the 7th day of pregnancy. On the 10th day, the rats were laparotomized under light anesthesia and the numbers of implantation sites and corpora lutea were noted. Results: Chromatographic pure principle from PE extract showed significant antiimplantation activity (60%) at the dose of 110 mg/kg, b.w while that from EAc extract showed 48.6 % effect at the same dose. In contrast, the final alcoholic extract showed no such significant action. Conclusion: The active principles from PE and EAc extracts showed significant antiimplantation activity and they were found to be a mixture of two groups of long-chain fatty acids from GLC.