Epididymal biopsy has been performed without consideration of the possibility of epididymal ductal severance and obstruction which result in obstructive azoospermia. An attempt was made to study the effect of the epididymal biopsy on the obstruction of the epididymal ducts. Bilateral epididymal biopsies were done in 8 healthy rabbits (New Zealand White strain) weighing over 3 kg, and then ejaculated semens have been analyzed 5 times every other week from 1 month after biopsies. Microscopic examination of the biopsied epididymides was also done after the 5th semen analysis. The results were as follows. 1. Semen analysis: 6 out of 8 rabbits showed azoospermia from the 4th semen analysis and 2 cases showed normal number of the sperms in the 5th semen analysis. 2, Microscopic examination: 6 cases of azoospermia showed complete obstruction of the biopsied sites of the epididymides, and abscence of sperms in epididymal ducts distal to the biopsied sites of the epididymides. However, recanalization of the epididymal ducts was noted in 2 cases showing normal sperm count. Therefore, it is concluded that the epididymal biopsy should be avoided in patients who want to be fertile, because it may cause the epididymal severance and obstruction of the epididymal ducts.