The pharmacokinetics of morphine were measured using gas chromatography-mass spectrometry (GCMS) with specific ion monitoring after the intramuscular administration of papaveretum to four patients with renal failure (one anephric) and three normals. The apparent t1/2 of absorption and t1/2 of elimination were significantly shorter in the patients with renal failure (P less than 0.05). Morphine glucuronides are eliminated slowly in these patients as expected. Renal failure does not impair the elimination of morphine.