Abstract A very easy, reliable and specific gas-chromatographic method for identification and dosage of 11 barbiturates in plasma is presented. Méthylene unit values determined on two types of column (one polar, one non-polar) allows very accurate identification with a minimum risk of error due to fluctuations in operating conditions. Sensitivity of the method is 0.5 μg/ml plasma with a flame ionization detector. Derivatization procedure is complete, without any degradation phenomenon as tested by mass spectrometry. Such a method can be easily used as routine procedure for toxicological or pharmacological applications.