The single dose pharmacokinetics of trifluoperazine (5 mg, Stelazine) were investigated in black (n = 25) and white (n = 32) healthy male subjects. Plasma samples were harvested over 24 h and analysed by a GLC-MS method. There were wide intersubject variations in all pharmacokinetic parameters examined, including Cmax, AUC, apparent oral volume of distribution at steady state, and elimination half-life. For each of these parameters the distribution was positively skewed in both blacks and whites and the geometric mean gave a better estimate of central tendency than the corresponding arithmetic mean. In all pharmacokinetic parameters examined there was no significant difference detected between black and white subjects or between smokers and non-smokers.