Sixteen laboratories participated in an intercomparison exercise carried out in 2003 on laboratory analyses of radionuclides in environmental samples. The sample types included seawater, lake water, soil, dry milk and seaweed and the exercise involved theradionuclides 137Cs, 90Sr, 60Co, 239, 240Pu, 241Am, 226Ra, 232Th and 40K. The evaluation of analytical performance was based on comparison with median values, a 10% target standard deviation and statistical tests at the 99% level. For 137Cs the resultsfrom 10 out of 16 laboratories passed the evaluation tests. For 90Sr the results from 5 out of 12 laboratories passed the evaluation tests. For 60Co, 239,240Pu and 241Am two laboratories submitted results and both passed the tests. For the naturalradionuclides 226Ra, 232Th and 40K, only a few laboratories did not pass the tests. For all radionuclides combined, the results from 6 out of 16 laboratories passed the evaluation tests. The results indicate that for several of the laboratories there isroom to improve the analytical quality on radionuclides in environmental samples to match an uncertainty corresponding to a relative standard deviation of 10%.