We examined semen characteristics of 128 patients prior to low-inguinal, spermatic vein ligation for varicocele and every 2 or 3 months over the course of a year. There was a higher sperm count 26 months after surgery, and after 68 months improved motility and a higher proportion of sperm with normal morphology. 10 months to 1 year after surgery there was improvement in all 3 parameters in 106 patients (82.8%), in 17 (13.2%) no change, and in 5 (3.9%) deterioration. Changes in sperm parameters (SP) were compared with retrograde flow (RF) into the pampiniform plexus 10-12 months after operation. Of the 106 patients with improvement in SP, only 14 (13.7%) had RF; of the 17 with no improvement, 14 (82.4%) had RF; and in all 5 in whom SP deteriorated there was bilateral RF. The study points to the necessity of continued follow-up of varicocele patients for at least a year after operation. Further management should be based on postoperative changes and the presence or absence of RF and improvement in SP.