Aminophylline (3 mg/kg i.v.) was injected in six patients with colicky pain caused by a ureter stone. In all but one this theophylline derivative caused a prompt and subjectively clear decrease in pain lasting from 30 min to 2 h. Serum levels over 12 microgram/ml were associated with good pain relief. A controlled study with an intravenous aminophylline infusion is warranted, because the pain-decreasing effect was too short-lasting after a single injection.