We have studied the disposition of alfentanil in six patients (who had suffered 10-30% surface area burns 5-21 days previously) undergoing surgical debridement and grafting and compared the data with those from a control group of six patients matched for age, sex and weight undergoing body surface surgery of similar duration. Plasma samples were collected up to 480 min after an i.v. bolus of alfentanil 50 micrograms kg-1. Drug concentrations were measured by radioimmunoassay and alfentanil binding to plasma proteins by equilibrium dialysis. The burns patients had significantly greater concentrations of alpha-1-acid glycoprotein (AAG) and smaller concentrations of albumin. The mean protein binding of alfentanil was 94.2 (SEM 0.05)% in the burns group and 90.7 (0.4)% in the control group (P = 0.004). There was a good correlation between AAG concentration and protein binding (r = 0.8). The volume of distribution and total clearance of alfentanil were reduced significantly in the burns group. The clearance of the unbound fraction and the elimination half-life of alfentanil were not decreased significantly.