Arctium lappa L. (burdock) is a plant brought from Japan and acclimated in Brazil, which is widely used in popular medicine all over the world. This study was carried out to assess the possible effects of A. lappa in testes of adult Wistar rats. They received the extract in water bottles at doses of 10 or 20 g/L daily for 40 days. There were no significant alterations in the biometric data including body and accessory sexual organs weight and in the histometric data such as volume density of the testis compartments and Leydig cell morphometry. Unaltered histometric and biometric data shows that A. lappa did not cause impairment of spermatogenesis.