Phenprocoumon was given orally to 9 patients with biopsy proven liver cirrhosis (dose range 0.12-0.25 mg/kg) and to 7 healthy volunteers (0.23 mg/kg). Concentrations of phenprocoumon were determined using HPLC in plasma and urine samples obtained for 6-7 days after drug administration. The binding of [3H]-phenprocoumon in plasma from all subjects was determined by equilibrium dialysis. Antipyrine plasma concentrations were determined spectrophotometrically following oral administration of antipyrine (1200 mg). The total body clearance of phenprocoumon was higher in the cirrhotic patients (1.64 +/- 0.16 ml/h/kg mean +/- SEM) than in the healthy volunteers (0.90 +/- 0.07 ml/h/kg), however the free drug clearance was not significantly different in the patients (144 +/- 14 ml/h/kg) compared with normal (113 +/- 11 ml/h/kg). In contrast the clearance of antipyrine was much reduced in the cirrhotic group (17.5 +/- 2.9 ml/h/kg) compared with normal (35.6 +/- 3.9 ml/h/kg). The metabolic clearance of phenprocoumon via glucuronidation, is relatively unaffected during cirrhosis compared with antipyrine clearance via oxidation.