Theophylline and antipyrine disposition has been compared in smoking epileptic patients, non-smoking epileptic patients and non-smoking healthy volunteers. Although clear differences in drug clearance and half-life were evident as a result of anticonvulsant drug therapy, no effect of smoking was discernible. Thus, additive effects from induction of the hepatic microsomal monooxygenase system in man by anticonvulsant drugs and polycyclic aromatic hydrocarbons (in cigarette smoke) were not evident.