Résumé : The method proposed here for the simultaneous determination of phenobarbital (PB), phenytoin (DPH), (CBZ) and primidone (PM) in biological samples is an improvement on other published flash-heater methylation methods. The two above-mentioned problems have been solved by the combination of appropriate internal standards (in particular, a new internal standard for CBZ), a modified rapid extraction procedure, and the use of a thermionic detector.