The secretion of sperm maturation-related molecules by the epididymis is subjected to developmental and hormonal regulation. In the BALB/c mouse, we found that GP-83 and GP-49, two sperm maturation-related glycoproteins, were secreted by the epididymis. The present study investigated the postnatal development and testosterone-dependence of these two molecules. Histochemical localization in paraffin sections revealed that wheat-germ agglutinin (WGA)-binding sites were first present in the epididymis of 4-week-old mice. The distribution of WGA-binding sites was the same as that of more mature mice, i.e., it was first found in the principal cells of the corpus epididymidis, and gradually appeared in the contents of epididymal tubules. On WGA blots, GP-83 and GP-49 were identified in the corpus, and GP-83 was identified in the cauda of the epididymis. In mice that had received unilateral orchiectomy at 4 weeks of age, GP-83 and GP-49 were present in both intact and orchiectomized epididymides 4 weeks after the operation. In the epididymides of mice that had received bilateral orchiectomy, GP-83 and GP-49 were barely identifiable. However, the presence of these two molecules was restored if testosterone was supplemented immediately after orchiectomy. These results indicate that GP-83 and GP-49 are secreted de novo in the epididymis, and that the secretion of these two molecules is developmentally regulated and androgen-dependent.