1 Plasma levels of benoxaprofen were measured in eight subjects 2-168 h after a single oral dose of 100 mg. Pharmacokinetic parameters were estimated by the NON-LIN computer programme using the two-compartment open model. Mean half-lives of absorption, distribution and elimination were respectively 0.4, 4.8 and 37.6 hours. Volumes of distribution were 6.8 and 3.2 litres for the central and peripheral compartments respectively. 2 Eleven subjects in groups of three or four were given 25 mg/day, 50 mg/day or 100 mg two times daily for 11 days. Their plasma levels were compared with those predicted from the above parameters, which were adjusted for individual body weights and elimination half-lives. Steady-state plasma levels were predicted in each case, and a resonable degree of accuracy (mean 91%) achieved. 3 There was no tendency for observed and predicted levels to diverge as the dose was increased, and there was no evidence of any change in the disposition of benoxaprofen on repeated dosing. 4 The pharmacokinetic parameters were used to predict steady state plasma levels for various dosage regimens.