Aim: To study the effect of vaseetomy on histological appearance of the testis. Methods: Parkes strain mice wereused as the animal model; they were bilaterally vasectomized (Vx) or sham-operated (So) and killed at intervals of 4,6, 9, and 12 months after the operation. Testes were excised from 5 Vx and 5 So mice at each interval and processed for histological examination. Results: Testes of So mice showed normal histological features. By contrast, marked al-terations were observed in the seminiferou tubules in testes of Vx mice, except in those killed 4 months after the opera-tion. The seminiferous epithelium in the tubules was only 2-3 layers thick and showed much depletion of germ cells;in severe cases, the epithelium consisted of only a thin layer of Sertoli cells, spermatogonia and a few spermatocytes.Exfoliation of germ cells, occurrence of multinucleated giant cells and vacuolated appearance of the epithelium were ofcommon features in the tubules. Furthermore, lumen of the rete testis in Vx mice w Aim: To study the effect of vaseetomy on histological appearance of the testis. Methods: Parkes strain mice were used as the animal model; they were bilaterally vasectomized (Vx) or sham-operated (So) and killed at intervals of 4,6, 9 , and 12 months after the operation. Testes were excised from 5 Vx and 5 So mice at each interval and processed for histological examination. Results: Testes of So mice showed normal histological features. By contrast, marked al-terations were observed in the seminiferou tubules in testes of Vx mice, except in those killed 4 months after the opera- tion. The seminiferous epithelium in the tubules was only 2-3 layers thick and showed much depletion of germ cells; in severe cases, the epithelium consisted of only a thin layer of Sertoli cells, spermatogonia and a few spermatocytes. Exfoliation of germ cells, occurrence of multinucleated giant cells and vacuolated appearance of the epithelium werecommon features in the tubules. furthermore, lumen of the rete t estis in Vx mice w