Lepidium meyenii (Brassicaceae), known as Maca, is a Peruvian hypocotyl that grows exclusively between 4000 and 4500 m above sea level in the central Andes. Maca is traditionally employed in the Andean region for its supposed fertility-enhancing properties. The study aimed to test the hypothesis that different ecotypes of Maca (Red, Yellow and Black) after short-term (7 days) and long-term (42 days) treatment affects differentially spermatogenesis adult rats. After 7 days of treatment with Yellow and Red Maca, the length of stage VIII was increased (P < 0.05), whereas with Black Maca stages II-VI and VIII were increased (P < 0.05). Daily sperm production (DSP) was increased in the group treated with Black Maca compared with control values (P < 0.05). Red or Yellow Maca did not alter DSP and epididymal sperm motility was not affected by treatment with any ecotype of Maca. After 42 days of treatment, Black Maca was the only ecotype that enhanced DSP (P < 0.05). Moreover, Black Maca was the only that increased epididymal sperm motility (P < 0.05). In relation to the control group, Red Maca did not affect testicular and epididymal weight nor epididymal sperm motility and sperm count; however, prostate weight was reduced (P < 0.05). Black or Yellow Maca did not affect prostate weight. In conclusion, there were differences in the biological response of the three ecotypes of Maca (Yellow, Red and Black). Black Maca appeared to have more beneficial effect on sperm counts and epididymal sperm motility. © 2005 Elsevier Ireland Ltd. All rights reserved.