A simple and specific reversed phase HPLC method for the determination of dinitrosopiperazine in simulated gastric juice using UV detection was reported. The chromatographic resolution of the analyte and the internal standard isosorbide dinitrate was performed without extraction from the gastric juice on a reversed phase ODS column. Isocratic elution was carried out with methanol-0.02 M sodium dihydrogen phosphate (60:40 v/v, pH 3.0) at a flow rate of 1.0 ml min(-1) with UV detection at 238 nm. The calibration graph was linear over the concentration range 0.072-2.88 microg ml(-1) of dinitrosopiperazine with minimum detectability (S/N=2) of 0.01 microg ml(-1) (8 x 10(-8) M). Inter-day and intra-day precisions calculated as % RSD were in the range 0.32-0.38% and 0.19-0.25% respectively. Inter-day and intra-day accuracies calculated as % error were in the range 0.18-0.21 and 0.08-0.11% respectively. The proposed method was successfully applied to the study of the possible in-vivo production of DNPZ under the standard nitrosation conditions recommended by WHO.