Studies with 85/287, a potent nonsteroidal antiestrogen/antiimplantation agent were taken up. In this paper we report alterations in uterine morphometric measurements and estrogen/progesterone receptor levels under the influence of this compound. Results showed 32% decline in stromal absolute volume density on day 5 post-coitum (p.c.) only, whereas eosinophilic leucocyte number decreased both on days 3 and 5 p.c. (41%) in treated rat uterus. Epithelial mitotic activity showed complete cessation both in control and treated rats on day 5 p.c. Under the influence of the compound both cytosolic and nuclear estrogen receptor (ERc and ERn) levels decreased on day 3 p.c., but on day 5 p.c. ERn increased significantly. A significant increase was however noticed in progesterone nuclear receptors (PRn) on day 5 p.c. On the whole our studies showed overall significant changes in uterine morphometric measurement/estrogen and progesterone receptor levels during the preimplantation period in rat under the influence of compound 85/287, causing asynchrony of events and thus failure of implantation.