A rapid quantitative and small scale method based on direct injection pyrolysis gas-liquid chromatography is described for the determination of N,N-dimethylalkylamine N-oxides. The method is suitable for determination of individual N-oxides as well as of their homologous compositions with or without the presence of parent tertiary amines in water or methanol solutions. The sensitivity of the method is 10-15 nmol of compounds injected. The unsymmetrical (1-methyldodecyl)dimethylamine N-oxide forms two isomeric alkenes 1-tridecene and trans-2-tridecene in a ratio of 1.68, in agreement with the predicted value.