A sensitive and specific capillary gas chromatographic method has been developed to measure trace amounts of 2,2'-dichlorodiethyl sulphide (sulphur mustard) in environmental or biological samples. Sulphur mustard was isolated from water or plasma by a solid-phase extraction procedure and from blood by liquid-liquid extraction. The accuracy and precision of the methods were demonstrated using replicate analyses of spiked water, plasma or blood: within-run and between-run variabilities were less than 20%. These analytical methods were used to evaluate the rate of sulphur mustard degradation in water or plasma. Good linear calibration curves, with a detection limit of 45 ng/ml, were obtained for quantitation and determination of sulphur mustard in blood following its intravenous administration to rats. Initial toxicokinetic data were obtained.