The case of a patient with pancreatitis in whom low theophylline concentrations were observed on oral aminophylline is presented. Therapeutic theophylline concentrations were obtained with intravenous aminophylline. However, serum levels following oral doses were only 20 to 40% of those observed with intravenous administration, suggesting malabsorption. The most reasonable explanation for this was the patient's pancreatic dysfunction, since adequate absorption of oral aminophylline had been demonstrated on a previous admission not associated with pancreatitis, and other possible causes of malabsorption were ruled out.