Objective: To investigate the effect of sildenafil citrate (Sc) on expressions of insulin like growth factor-1 (IGF-1) and basic fibroblast growth factor (bFGF) which are two of the factors taking part in endometrium receptivity in implantation window period in rats which controlled ovarin hyperstimulation (COH) was performed. Material and Methods: In our study, three months old, 220-250 gram weighted female Wistar albino rats were used. Those were divided into four groups as control, COH, Sc and COH+Sc groups. Rats were put together with male rats for copulation on the fourth day following administrations, lasting for three days according to their groups. Rats with spermatozoa in their vaginal smear the next day were accepted as on the zeroth day of pregnancy. Rats on the third, fourth and fifth day of pregnancy were sacrificed. Their uteruses were resected, cross-sections were stained with immunohistochemical method and examined. Results: On the third day, the most intensive IGF-1 immunoreactivity in glandular epithelium was detected in COH+Sc group, where as it was detected in luminal epithelium and stromal cells in Sc and COH+Sc groups. While immunoreactivity in luminal epithelium was significantly high in Sc group on the fourth day, the most intensive IGF-1 immunureactivity in luminal epithelium, glandular epithelium and stromal cells was in Sc group on the fifth day. The most intensive bFGF immunureactivity was detected in Sc group in luminal epithelium and stromal cells and in Stand COH groups in glandular epithelium on the third day. On the fourth day, while bFGF immunoreactivity in luminal epithelium was significantly intensive in Sc group, it was prominent in glandular epithelium, stromal cells, endothelium and myometrium in Sc and COH groups. On the other hand, bFGF immunoreactivity in luminal and glandular epithelium was detected intensively in Sc group on the fifth day. Conclusion: Our results showed that sildenafil citrate took part both in implantation and decidualization by affecting IGF-1 and bFGF expressions in implantation window period in rats.