The histomorphological features of the uterus of three months old mice (after puberty), previously to 17-B Bstradiol (E) or different doses of technical grade Methoxychlor (T.g. Mx), was investigated. Early as one day-old, the neonates received a daily intraperitoneal injection for 14 successive days with a sterile sesame oil containing 10 ug (E), or 0.1, 0.5 & 1.0 mg (T.g. Mx) as treated groups, or sesame oil vehicle only as a control group. The 0.5 mg (Mx)-dose significantly decreased the weight of the reproductive tract of mice after puberty. The (E)-induced histological alterations were disorganization and focal metaplasia of endometrial and glandular epithelia. Cystic formations of some endometrial glands, and appearance of pale-stained cells throughout the disorganized glands, stroma and myometrium were also observed. The (Mx) - resulted changes were epithelial hyperplasia, disorganized endometrial glands, cystic glandular units with apppearance of epithelial metaplasia in both endometrial and glandular epithelium. These alterations were increased at the highest (Mx) - doses.