To know the role of sex hormone-binding globulin (SHBG) in the intracellular steroidal actions in human ovarian cancers, the expression of SHBG mRNA as a substitute for intracellular SHBG expression was investigated in normal ovarian tissues and ovarian tumors. In the present study, we used competitive reverse transcription-polymerase chain reaction-Southern blot analysis to evaluate SHBG mRNA levels. The expression of SHBG mRNA was detected in all normal ovaries and benign and malignant ovarian tumors analyzed. There were no significant differences in the mean SHBG mRNA levels among the three types of tissue. The expression in normal ovaries was significantly higher (p < 0.01) in premenopause, suggesting the predominance of a sex steroid hormone effect on ovarian SHBG synthesis. Relative overexpression of SHBG mRNA was observed in six out of 22 cases (27%) of ovarian cancer (three cases of endometrioid adenocarcinoma, two cases of serous cystadenocarcinoma and one case of mucinous cystadenocarcinoma) in comparison with normal ovaries and benign ovarian tumors. There was no difference in expression among the clinical stages of ovarian cancers. These data suggest that normal human ovaries and ovarian tumors might synthesize SHBG intracellularly, ovarian cancers might conserve an estrogen-associated property via SHBG and the regulation of intracellular SHBG expression might be changed in some cancers.