A double-blind clinical trial was carried out to evaluate the efficacy of pirenzepine (PZ) in acute pancreatitis (AP). One hundred and fifteen patients were randomly allocated in three groups, comparable in number, clinical and biochemical parameters. All were hydrated and received nasogastric suction. Group A was the control, groups B and C received additionally 10 and 20 mg of PZ intravenously every 12 h, respectively. PZ-treated patients showed benefit, with a significant difference (p less than 0.01) in the duration of hyperamylasemia and the duration of pain tending to be significantly reduced (p = 0.054). PZ influenced significantly (p less than 0.01) the plasma amylase levels and caused no major adverse effects. Complications were less frequent and mortality was reduced in patients who received PZ. Thus, the use of PZ in AP appears to be beneficial and safe; however, these preliminary results deserve further confirmation before a general recommendation to treat such patients can be made.