Ultrastructure of the membrana propria and the seminiferous epithelium was studied in infertile human testis both before and 3-6 months after varicocelectomy. The frequent alterations, observed before and after the operation, were extremely thickened membrana propria, deep invaginations, multilamination and knob-like formation of basal laminae and formation of multinucleated spermatids, which were all considered as the common response of the testis to different noxious agents. Although the cells of the seminiferous epithelium were clearly affected by varicocele before varicocelectomy, many areas exhibited normal features after the operation. Furthermore, multinucleated cells, sharing common features of Sertoli cell and spermatogonium, were observed, as well as presence of well-developed annulate lamellae in the Sertoli cells, exhibiting centrioles in the vicinity of their nuclei after varicocelectomy. These multiple ultrastructural observations indicate that Sertoli cell division takes place. This study suggests that if the observation period of the tissue samples after varicocelectomy is long enough, the reversible changes of the tubular cells would be seen much more frequently.