Inductively coupled plasma mass spectrometry was used to det. contents of La, Ce, Pr, Nd and Eu in waters from various sources to establish the applicability limits of the anal. method. The detection limit reached 0.005 mu g/L for Ce, Eu, La and Pr, 0.006 mu g/L for Sm and 0.007 mu g/L for Nd. The quantification limit of 0.02 mu g/dm(3) was achieved for all tested elements. Furthermore, the precision and accuracy of the method were in accordance with international stds.