Valerian (Valeriana officinalis L.) is a natural anxiolytic widely used in traditional medicine. However reproductive toxic effects have been demonstrated in mice treated with this species. This study evaluated the effect of valerian aqueous suspension on the reproductive system of Wistar rats treated for 53 days. Four groups were studied (n=25): control (1 ml of distilled water) and treated (500, 1000 or 2000 mg/kg) with the aqueous suspension per os/day. On the 54th day, 15 rats/group were killed and the following parameters were assessed: weight of reproductive organs, liver, kidneys and spleen; serum testosterone level, sperm morphology and concentration; testicle and epididymis histomorphometry. Ten other animals/group was analyzed using the dominant lethal test. There were not significant differences in body weight, hematological and biochemical parameters, weights of the liver, kidneys, spleen, reproductive organs and accessory glands between control and treated animals. The treatment with valerian did not alter the tubular and luminal diameters of the seminiferous tubules, the serum testosterone levels and the sperm viability. The sperm concentration in the epididymis cauda was not altered by the treatment although a significant increase in the number of abnormal gametes was observed in the valerian-treated animals at all dose levels when compared to control values. Significant reduction (p<0.05) in the height of the epididymal epithelium and a significant increase in the number of abnormal gametes were observed in the animals treated with the extract at 1000 and 2000 mg/kg.