A high performance liquid-chromatographic procedure is reported for measuring the plasma concentration of 5 anticonvulsants: phenobarbital, phenytoin, carbamazepine, ethosuximide, valproic acid and 2 bronchodilators: theophylline and caffeine. Limits of detection of ethosuximide and valproic acid are 28 mumol/l, 5 mumol/l for the other drugs. Linearity limits are always very upper than the higher therapeutic dose concentration, the inter assay relative standard deviation are less than 8 p. cent for the 7 drugs at the 3 levels of concentration and the analytical recoveries ranged from 93 to 104 p. cent. The technique is simple and rapid: 4 anticonvulsants are simultaneously extracted and dosed, valproic acid, only has to be dosed lonely. Finally, comparatively to the other immunoassay technique, this method is cheaper.