AbstractRats were subjected to pre‐ and postnatal undernutrition by restricting the food intake of their mothers (U); another group of rats was normally fed (N). Each nutrition group was divided into 3 subgroups by varying the degree of environmental stimulation: animals in the Max group were stimulated by handling and enriched rearing conditions; the Min group rats were subjected to social isolation; rats in the control condition (C) were raised under ordinary laboratory conditions. The onset of sexual activity was not affected in the U‐C male rats, but was delayed in both U‐Min and N‐Min rats. Although no difference existed in the age of puberty between the N‐Max and N‐C animals, the U‐Max rats displayed an advancement of puberty by 7 days in comparison to the U‐C rats. Undernutrition did not affect female sexual maturation; however the Max condition delayed this process in both n