The authors have followed for up to 32 months 51 oligospermic patients with varicoceles who underwent high ligation and division of the left spermatic vein. Of these patients 59.9 per cent had improvement in total sperm count, 47.1 per cent in sperm motility and 42.1 per cent in the morphological pattern of the spermatozoa. Pregnancies were reported by 13 patients. Improvement in sperm motility occurred first followed by improvement in morphology. The last improvement was in total sperm count. The authors suggest that the observation period after a varicocele operation be restricted to 9 months, in which time about 75 per cent of the expected improvement takes place. A clinical classification for the degree of varicocele is proposed. No correlation between size of the varicocele and treatment results could be observed.