5-aminosalicylic acid has been reported to cause acute pancreatitis. We report the first Scandinavian case. A 27 year-old woman with a three month history of ulcerative colitis treated with Mesalazine developed acute abdominal pain. Serum and urine amylase were raised, and ultrasonographic and computed tomography scan showed oedema of the pancreas. Immediately following withdrawal of the drug, serum and urine amylase returned to normal. We discuss the possibility of acute pancreatitis as an extraintestinal manifestation of ulcerative colitis.