The influence of prolonged exposure of guinea pigs to excessive ascorbic acid (AA) on the outcome of pregnancy, as well as the adaptive effect of the vitamin either during preweanling life or following weaning, were examined. Continuous exposure to AA (1 mg/mL drinking water) from the time they were first mated up to the time of second pregnancy, had no significant effect on the number of offspring and on their weights at birth, when compared with that of the animals receiving 0.1 mg AA/mL drinking water. However, change in AA intake from 1 to 0.1 mg/mL drinking water, at the age of 21 days, resulted in a significant loss in body weight and reductions in the plasma, leukocyte, and adrenal concentrations of AA, as compared with those of the pair-fed animals receiving 0.1 mg/mL drinking water throughout. The present study also indicated that the conditioning effect is less pronounced in guinea pigs when exposed to the high AA following weanling age than in utero.