Ovarian surface epithelial (OSE) cells participate in the formation of the ovarian cortex and are potential targets of oestrogen action. Oestrogens typically act through nuclear oestrogen receptors (ER) of which there are two known subtypes: ERalpha and ERbeta. In view of the potential importance of oestrogen as a local regulator of OSE cell function, we screened for ERalpha and ERbeta mRNA in primary OSE cell cultures by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis, and used freshly isolated granulosa cells (GC) and granulosa-lutein cells (GLC) as positive controls. OSE cells, scraped from the ovarian surface of women undergoing laparotomy for benign gynaecological conditions, were cultured for up to 21 days to obtain enough cells for mRNA extraction. GC were obtained from spontaneously cyclic women undergoing total hysterectomy; while GLC were obtained from follicular aspirates of gonadotrophin-stimulated in-vitro fertilization patients. Total RNA (1 microg) was reverse transcribed into single-stranded cDNA for PCR (30 cycles) using primers selected to give specific ERalpha and ERbeta products. The ERalpha and ERbeta PCR products, authenticated by cloning and sequencing, were both weakly detectable by Southern analysis in cultured OSE cells and readily detectable in GC and GLC. These results show that cultured human OSE express both ERalpha and ERbeta mRNA, consistent with a role for oestrogen in the regulation of OSE cell function in vivo.