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 $600mu extrm{m}$ pieces, and cultured in the sandwich agar bed system for 21-23 days. Estrone ($E_{1}$) and estradiol-17 $eta$($E_{2}$) in the medium was measured by radioimmunoassay. Amount of $E_{2}$ synthesis was greater than $E_{1}$ in both normal cases. In contrast, fetal ovaries from anencephalic fetus did not produce neither $E_{1}$ nor $E_{2}$ 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.