A high performance liquid chromatographic method for determination of Ethionamide (ETH) in human plasma was developed. The method involved deproteinisation of the sample with perchloric acid and analysis of the supernatant using a reversed-phase CN column (150mm) and a wavelength of 267 nm. The mobile phase consisted of Milli-Q water and Methanol (85:15, v/v) containing 0.05% Perchloric acid and 0.1% tetrabutyl N-ammonium hydroxide. The assay was specific for ETH and linear from 0.25 to 10.0μg/ml. The relative standard deviation of intra- and inter-day assays was lower than 10%. The average recovery of ETH from plasma was 91%. Due to its simplicity, the assay can be used for pharmacokinetic studies of ETH and to check patient adherence to tuberculosis treatment.