Intraluminal pancreatic enzymes influence intestinal function, adaptation, and susceptibility to injury. These effects may be mediated partly through changes in the rate of epithelial cell turnover. We assessed intestinal morphology and cytokinetics in a rat model of exocrine pancreatic insufficiency that does not alter anatomic relationships or animal growth. Pancreatic duct occlusion was performed by applying metal clips on both sides along the common bile duct. Control animals underwent sham-operation with exposure and manipulation of the pancreas without duct occlusion. Twelve days later, pulse labeling with tritiated thymidine was performed, and mitotic arrest was induced with colcemid. Groups of animals were sacrificed at 0 and 2 hr after colcemid injection. Specimens for histopathology, morphometry, and autoradiography were obtained from duodenum, proximal jejunum, distal jejunum, and ileum. Labeling index, grain counts, mitoses per crypt, cells per crypt, cells per villus, crypt depth, villus height, and number of goblet cells per villus were used as end points. Pancreatic duct occlusion resulted in increased labeling index across intestinal segments relative to sham-operated controls (P < 0.01) and increased labeling index and mitotic rate in distal compared to proximal intestine (P < 0.05). Grain-count histograms were similar in the two experimental groups. There were no significant morphologic differences between pancreatic duct-occluded animals and controls. Exocrine pancreatic insufficiency increases crypt cell proliferation in distal small intestine but does not alter the duration of S phase. These changes are most likely due to an increase in the size of the proliferative compartment and may be partly responsible for changes in small bowel function and response to injury.