The present study was conducted to determine the effect of recombinant human follicle stimulating hormone (rhFSH) on the estrogen synthesis by human fetal ovarian tissues. Fetal ovaries were 18-19 weeks old (18 wks:n=1, 19 wks:n=2). One case of 19-week-old fetal ovaries were obtained from anencephalic fetus. Obtained ovarieswere cleaned and diced around pieces, and cultured in the sandwich agar bed system for 21-23 days. Estrone () and estradiol-17 () in the medium was measured by radioimmunoassay. Amount of synthesis was greater than in both normal cases. In contrast, fetal ovaries from anencephalic fetus did not produce neither nor in the presence or absence of rhFSH. Results suggest that the fetal ovaries have a capacity of estrogen production at 18-19 weeks of gestation Existence of FSH receptor is also supposed. Different results by anecephalic fetal ovaries suggest the difference in the development between normal and anencephalic fetal ovaries.