The pharmacokinetics of a single oral dose of buspirone (20 mg) were determined in 12 patients with cirrhosis and 12 normal subjects. The mean AUC of buspirone was 55 +/- 38 s.d. ng ml-1 h in cirrhotics and 3.5 +/- 2.4 s.d. ng ml-1 h in normals. The time until maximum concentration (tmax) attained was similar in the two groups (0.6 vs 0.7 h), but mean maximum concentration Cmax was higher in patients (18.8 +/- 16.3 s.d. ng ml-1) than in normals (1.2 +/- 0.8 s.d. ng ml-1). Mean elimination half-life of buspirone was greater in cirrhotics, but this difference was marginally significant statistically (cirrhotics, 6.1 +/- 3.5 s.d. h, normals 3.2 +/- 1.5 s.d. h, P = 0.05). Eight of 12 patients and seven of 12 normal subjects had a second peak in the plasma concentrations of buspirone. In patients this occurred at 10.8 +/- 7.4 s.d. h after the dose, and its mean concentration was 3.1 +/- 6.6 ng ml-1. In normal subjects the second peak occurred at 4.3 +/- 2.1 h after the dose and its mean concentration was 0.5 +/- 0.3 ng ml-1. On the kinetic evidence buspirone should be used with caution in liver disease.