Intraoperative internal spermatic vein phlebography was performed in 20 subfertile patients with a varicocele; 10 patients with varicoceles and left-sided indirect inguinal hernias without fertility problems served as controls. Phlebography was carried out during surgery with the patient supine and in a 45 degree anti-Trendelenburg position to stimulate an "erect" posture. In all 25 patients with a varicocele, valvular insufficiency was demonstrated at the renal-spermatic vein junction. When visualized, the position of the left adrenal vein in all instances was medial to or opposite the renal-internal spermatic vein confluence. This observation, reinforced by simultaneous determinations of cortisol levels in the internal spermatic and antecubital veins, practically excluded the validity of the theory of adrenal hormonal suppression of testicular tissues. In 40% of subfertile patients with a varicocele, double internal spermatic veins and reflux to the distended external spermatic (cremasteric) venous plexus were demonstrated. In no instance were such phenomena observed in the control groups. The not-infrequent failure of operative correction of varicocele seems to relate directly to such overlooked pathology. Broad clinical application of operative phlebography, especially in recurrent, persistent, or clinically advanced cases, will detect such anomalies and should reduce significantly the operative failures in the surgical correction of varicocele.