Spermatic vein specimens were removed from 46 patients with varicocele who underwent high ligation of the left spermatic vein and 11 men with renal cancer who underwent radical nephrectomy. Semen analysis was performed preoperatively and after 3 months, and the contents of noncollagenous protein, collagen and elastin in the spermatic vein were determined. The noncollagenous protein contents in the spermatic vein were greater in patients with grades 2 and 3 varicocele than in those with renal cancer (p < 0.001) and grade 1 varicocele (p < 0.01), respectively. Similar results, to a lesser extent, were also obtained for the contents of collagen. The content of elastin in each group was identical. Noncollagenous protein content correlated inversely with sperm count and sperm motility in all varicocele groups, as did collagen content in patients with grades 2 and 3 varicocele. These results indicate that there is an association between a large amount of noncollagenous protein and collagen in the spermatic vein and deterioration of the spermiogram in patients with grades 2 and 3 varicocele.