A new analytical technique using ICP-MS was applied to the determination of237Np in some environmental samples. The accuracy and precision of the new method were assessed by comparison with those of conventional NAA and -spectrometric method as well as by analysis of the intercomparison sample of Ravenglass NRPB silt. The results obtained by ICP-MS were in good agreement with those by NAA or
-spectrometry at a relative deviation of 2–9%. The detection limit is 0.02 mBq/ml (26 mBq=1 ng).