Epididymal sperm maturation in the stallion was analysed using eight epididymides and deferent ducts from healthy animals. Samples were obtained in June-July and October-November (resting and breeding periods, respectively). Epididymides were divided into head, body and tail. Sperm samples were submitted to a routine seminogram, chromatin decondensation test (Lung, 1972) and sperm velocity determination (Makler, 1980). Results demonstrate that stallion spermatozoa achieve maturation in the transition between the head and body of the epididymis as revealed by chromatin decondensation. Objective and subjective motility and sperm velocity acquire maximal values in the cauda epididymis where they are similar to the values seen in the vas deferens. No differences were found in the proximal and medial segments of the epididymis regarding these parameters when sexually active and resting animals were compared.