In a histomorphological study of the vagina of sixty-six sows of documented ages, known genetic background and dietary history, it was noted that a sub-epithelial elastic layer appeared after 1 year of age in the vaginal mucosa. Above 2 years of age, epithelial folds or invaginations were seen in the tunica mucosa as microcysts or cell nests. The inner circular layer of tunica muscularis consisted of equal amounts of fibrous tissue and smooth muscle, forming a fibromuscular layer. The ductus epoophori (canal of Gartner) persisted up to 8 years of age (maximum age studied). Evaginations as outgrowths of the epithelium of this canal were augmented with advancing age. The clinical or pathological significance of these mesonephric remnants in the vaginal wall of the aged sow should be borne in mind when diagnosing neoplasms of the vagina. Most of the vaginal arteries did not seem to be affected with intimal thickening to any great extent when compared to the arteries of the uterine tubes, uterus and cervix of the corresponding age groups.