The multiple-dose kinetics of dapsone (DDS) and its principal metabolite monoacetyldapsone (MADDS) were determined in 6 healthy volunteers after daily administration of low-dose dapsone (10 mg). Comparison with a previous study involving the same volunteers on a daily regimen of proguanil (200 mg) plus dapsone (10 mg) revealed no statistically significant differences in the maximum plasma concentrations, area under the plasma drug concentration curves and elimination half-lives of both DDS and MADDS in the presence of proguanil. Although these findings suggest that proguanil does not alter the pharmacokinetics of DDS and MADDS, the possibility that proguanil affects the disposition of hydroxylated metabolites of dapsone, which appear to mediate dapsone toxicity, cannot be excluded.