Abstract: If the tissue or organ have 3-β-hydroxy steroid dehydrogenase (3-β-HSDH), they can synthesize the steroid hormone. According to that idea, we have studied the distribution of 3-α-HSDH in the female reproductive system of rats and mice, human endometrium and decidua with histochemical techniques. The results as follows: 1. The granular lutein cells and the theca lutein cells have showed a strong positive reaction. Theca interna cells and metrial gland cells were middle positive staining in the ovary of rats and mice. 2. The glandular epithelium and the surperficial epithelium showed moderate positive reaction. 3. The glandular epithelium and the big decidual cells of human decidua were moderate positive. 4. We did not look for a positive endometrial cells in human endometrium. The present study have been idenlified that the uterus of rats and mice, and the endomitrial cpitheliums and big cells of women＇s decidua possessed the funetion to secrete Steroid hormones. We proposed that the uterus of rat and mice and human decidua may be a endocrine organ.

Key words: histochemistry, 3-β-HSDH, endometrium, decidua