Varicocele is the most common cause of primary male infertility and is associated with oxidative stress. The aim of the present study was to investigate the effects of anthocyanin on a rat model of varicocele. Twenty-four male rats were divided into four experimental groups: a normal control group, a varicocele-induced control group and two varicocele-induced groups treated with either 40 or 80mgkg(-1), p.o., anthocyanin for 4 weeks. Varicocele was induced by the partial obstruction of the left renal vein. After 8 weeks, the testes and epididymides from rats in all groups were removed, weighed and subjected to histological examination and semen analysis. Apoptosis in the testes was determined by terminal deoxyribonucleotidyl transferase-mediated dUTP-digoxigenin nick end-labelling (TUNEL) and oxidative stress was assessed by measuring 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels. Although no significant differences in sperm counts were observed among the groups, anthocyanin treatment of the varicocele-induced groups resulted in significantly increased testes weight, sperm motility and spermatogenic cell density (P<0.05). Anthocyanin treatment also significantly decreased apoptotic body count and 8-OHdG concentrations (P<0.05). We suggest that the antioxidant effect of anthocyanin prevented the damage caused by varicocele-induced reactive oxygen species.