We retrospectively reviewed the charts of all patients with acute pancreatitis admitted to our hospital between July 1987 and June 1991 to determine the relationship of a pleural effusion in patients with acute pancreatitis with the severity of the disease, the etiology of the pancreatitis, pseudocyst formation, and triglyceride levels. Eleven (13.4%) of the 82 patients with acute pancreatitis had evidence of pleural effusion. Eight of 42 patients with alcoholic pancreatitis developed an effusion, compared with one of 33 patients with biliary pancreatitis, indicating that an alcoholic etiology may be a risk factor. Seven (63%) of the 11 patients had associated pseudocysts. Patients with severe disease had a greater incidence of pleural effusion. The effusion was on the left side in six, bilateral in four, and on the right side in one patient. Hypertriglyceridemia did not appear to be an independent risk factor associated with pleural effusions. Diagnostic thoracentesis was performed in three patients because of the presence of fever. Pleural fluid amylase was normal in one case and mildly elevated in the other two. All effusions resolved spontaneously without the need for any therapeutic intervention.