The sensitivity and precision of the determination of trace amounts of lead can be improved significantly with a combination of continuous hydride generation, isotope dilution and inductively coupled plasma mass spectrometry (ICP-MS). Both the conventional Thompson U-shaped and a microporous polytetrafluoroethylene (PTFE) tube gas-liquid separator were evaluated. The limit of detection for lead was restricted to the range 0.01–0.05 µg l^–1 by the reagent blanks. Iron and copper ions exhibit a serious interference on the lead hydride generation. Sulphosalicylic acid and sodium cyanide, dissolved in sodium tetrahydroborate (III) solution, were used to eliminate the iron and copper interferences, respectively. Lead in National Bureau of Standards (NBS) Standard Reference Material (SRM) Trace Elements in Water (1643a) was determined by the isotope dilution-hydride generation technique. Good agreement was obtained between the certified and the experimental results. Lead isotope abundances were also determined for NBS SRM 981 Common Lead and various galena samples.