The function of the exocrine pancreas was studied in rats in which more than 50% of the glandular tissue had been resected 1 (n = 16) or 6 (n = 20) weeks before initiation of the study. Sham-operated animals served as controls (n = 15). After partial pancreatectomy, the weight and DNA content of the remaining gland increased significantly (p less than 0.001), and the digestive enzymes: DNA content ratio was temporarily elevated. The glandular tissue secreted relatively less fluid, bicarbonate and digestive enzymes than in control animals, but the outputs increased significantly (p less than 0.001) during the observation period. After 6 weeks, only the fluid and bicarbonate secretion was still reduced. It is concluded (a) that the pancreatic function recovers after partial resection; (b) that the enzyme output of the remaining glandular tissue decreases temporarily; (c) that the enzyme content of the gland thereby increases, and (d) that the function of the acinar cells recovers faster than that of the ductular system.