The effects of cirrhosis on the elimination kinetics and plasma protein binding of sufentanil were evaluated in 12 anesthetized patients with uncomplicated cirrhosis and these findings were compared with data from age-matched control anesthetized patients with normal hepatic and renal function. Sufentanil 3 micrograms/kg was given intravenously as a bolus injection and venous plasma concentrations were measured at intervals up to 10 hrs. The average (+/- SD) elimination half life was 3.5 +/- 0.9 hrs in controls and did not differ in cirrhotics: 4.1 +/- 0.6 hrs. The plasma clearance did not differ between the two groups: 11.3 +/- 2.5 ml.min-1.kg-1 in controls and 10.8 +/- 4.6 ml.min-1.kg-1 in cirrhotic patients. The sufentanil free fraction was also similar in controls (8.3 +/- 1.5%) and in cirrhotic patients (9.6 +/- 1.8%). These data suggest that sufentanil in a single dose should have a similar duration of action in patients with uncomplicated cirrhosis and in normal patients.