Several parameters of the reproductive function were studied in albino rats of the Wistar strain fed an essential fatty acid-deficient (EFAD) diet, a linoleic acid-sufficient (EFAS) diet or a commercial diet (CD). The frequency of irregular estrous cycles, with an increased incidence of prolonged diestrus, was significantly higher in EFAD and EFAS groups than in the CD group. There were no significant differences between EFAD and EFAS rats in any of the estrous cycle parameters studied. The EFAD rats showed the following changes in reproductive performance in respect to EFAS and CD dams: prolonged period of gestation, reduced litter size and increased pup mortality during delivery and the first 48 neonatal hours. From this time to weaning, EFAD and EFAS pups had a similar rate of mortality and were different in this respect from the CD group. These results support previous reports indicating that linoleic acid is essential to the maintenance of normal pregnancy and the survival of newborn rats. Nevertheless, we cannot conclude that impairment of the estrous cycle and sucking mortality until weaning were primarily due to the absence of linoleic acid in the maternal diet. The possible role of alpha-linolenic acid in the reproductive is discussed.