Malnutrition is worldwide. Irreversible effects on the pancreas and pancreatic function when studied clinically have been contradictory. This laboratory experiment was designed to study the pancreas under conditions of severe malnutrition over a long period of time. Its purpose was to determine whether organic as well as functional changes are reversible in young animals as they mature, and in animals deprived in utero. Dramatic decreases in enzyme levels as well as protein and DNA occur with severe protein restrictions. Electron microscopy and H&E sections show no abnormalities and all measurements return almost to normal levels after refeeding. Animals deprived of protein in utero although severely malnourished at birth have excellent functional recovery of enzyme content after 13 to 19 weeks on a normal diet and a return to almost normal growth curves.