A method for the measurement of malondialdehyde (MDA) using GLC with a nitrogen phosphorus detector (GLQNPD) is described and evaluated. The method uses 2-hydrazinobenzothiazole (HBT) which forms condensation derivatives with MDA, acetoacetaldehyde, and acetylacetone (AA). GC/MS and "C NMR studies of the three derivatives obtained showed that they are 2-(pyrazol-I'-yl)benzothiazoles and that they can be separated by GLC/NPD. Any one of these derivatives can be used as an internal standard for the measurement of the other two. The optimal conditions for the measurement of MDA were. studied. At pH 2.5 and 7o'C, the condensation derivative is quantitatively formed in 30 min. Its extraction is obtained by a mixture of n-hexanelisoamyl alcohol 98/2 (v/v) containing HBT-AA as internal standard. The GLC detection limit is 0.04 pmol. Inter-and intraassay coefficients of variation were 2.9 and an average of 4.0%, respectively. The method is specific, and there was no interference from other carbonyl compounds. The artifactual formation of MDA from carbohydrates during the derivatization reaction is negligible. The method is proposed as a reference method for the standardization of working solutions of MDA or MDA-generating solutions. o 1988 Academic PESS, IIW.