Parameters of nutritional and small intestinal status were studied in 3 groups of rats which had been subjected to malnutrition during different periods (pre- and postnatal, postweaning and adulthood). Malnutrition was induced by restriction of feeds (50% of controls). Compared with controls, malnourished rats from all 3 groups had reduced body weight and length, thoracic diameters, small intestinal weight, length and diameters, small intestinal mucosal weight, total mucosal DNA and protein/DNA ratios. However, there was no difference in DNA contents between malnourished rats and corresponding controls, indicating no changes in cell number (hypotrophic). Prenatally malnourished rats had reduced specific activities of lactase, sucrase and maltase. But in other malnourished groups, the activities of these enzymes were higher compared with corresponding controls. Prenatally malnourished rats had the lowest percentage of control values in all parameters measured compared with the other malnourished rats.