The cellular expression of pituitary gonadotropin receptors in gonadal tissues is poorly defined because of the lack of suitable reagents. In this study, we developed in situ hybridization and reverse transcription polymerase chain reaction techniques for the evaluation of follicle-stimulating hormone receptor (FSHR) expression in the ovary and fallopian tube. Using a single-strand RNA probe, we demonstrated that FSHR mRNA expression is strongest in Graafian follicles. Within these developing follicles, granulosa cells showed the greatest expression, although both theca interna and theca externa were also positive, interna greater than externa. Granulosa cells in both primary and primordial follicles were positive, with primordial follicles showing only weak focal positivity. Ovarian surface epithelium and fallopian tube epithelium, not previously recognized to express FSHR, were both strongly positive. The FSHR expression in the ovary and fallopian tube was confirmed by reverse transcription polymerase chain reaction. Our results indicated that the FSHR is expressed in a cell-specific fashion at different stages of follicular development and is also expressed in ovarian surface and fallopian tube epithelia. The presence of FSHR in ovarian surface epithelium and of gonadotropin-binding sites in ovarian neoplasms provide additional evidence supporting the derivation of epithelial ovarian tumors from the surface epithelium and should promote heightened interest in the gonadotropin theory of ovarian tumorigenesis. More importantly, this study shows the feasibility of evaluating FSHR expression by both in situ hybridization and reverse transcription polymerase chain reaction. Application of these techniques to tumor specimens will help to elucidate the role of gonadotropins and their receptors in the carcinogenesis of gynecological tumors.