The pharmacokinetics of ximoprofen were studied in young and elderly subjects after single and repeated doses up to 30 mg. In healthy elderly subjects (30 mg dose), a mean peak plasma drug concentration of 1.78 micrograms ml-1 +/- 0.83 s.d. occurred at a mean time of 1.95 h +/- 1.40 s.d. and, thereafter, concentrations declined monoexponentially with a mean half-life of 3.8 h +/- 1.4 s.d. Comparison of these data with those from younger healthy subjects showed that peak drug concentrations, areas under the curve and half-lives were about two-fold greater in the elderly, these differences probably reflecting a lower systemic drug clearance. Similar results were obtained on comparing data from young healthy subjects and elderly rheumatic patients receiving single and repeated doses of ximoprofen (15 mg twice daily). In patients, the half-life of ximoprofen was 2.5 h +/- 0.7 s.d. Within either group, pharmacokinetic parameters after single or repeated doses were similar: ximoprofen did not accumulate in the plasma of the young or elderly.