Our experiences with 343 vaso-epididymal anastomosis operations carried out for the relief of obstructive azoospermia in the past 20 years were reported. The etiologic factors in obstructive azoospermia were discussed. Smallpox was the single most common factor responsible for the obstructive lesion in our series. Obstructive azoospermia due to congenital anomalies was very infrequent. The pathologic physiology of obstructive azoospermia was reviewed. In 37 patients vaso-epididymostomy could not be carried out because of some genital pathology or congenital abnormality. Vaso-epididymal anastomosis was performed in the remaining 281 patients. The operation was succesful in 137 patients (48.75%), and pregnancies occurred in 40 instances (14.23%). However, even after successful operations, the postoperative sperm counts were above 20 million/ml in only 56 patients (19.93%). Persistent necrospermia resistant to treatment was noted in 48 patients (35.04%). In 71 patients (51.83%), spermatozoa appeared in the semen within the first 3 months after operation, but, in 17 patients (12.41%), the appearance of spermatozoa in the semen was delayed for 1 year or more. Twenty patients (7.11%) again became azoospermic after a variable length of time. In this series, bilateral operations were performed on 185 patients and unilateral operations were performed on 96 patients. Our results indicated beyond doubt that bilateral operation is the method of choice. In addition, an analysis of our data showed that operations performed with an internal nylon splint yield more satisfactory results.