Exocrine pancreatic function and fat absorption were determined using a 'tubeless' test in 25 human immunodeficiency virus (HIV) antibody positive subjects (23 males, two females), CDC criteria groups II (four), III (one), and IV (20). In 12 fat absorption was poor but in only three of these were the results indicative of pancreatic insufficiency and in all three this was mild. In nine of the cases the results were compatible with small intestinal malabsorption. Mild, but not severe, exocrine pancreatic insufficiency may occur in acquired immune deficiency syndrome; however fat malabsorption is more commonly associated with a small intestinal cause.