The "1st South-Eastern European Interlaboratory Study WATER ANALYSIS-2003" was organized in the period of November 2003 to February 2004, on the basis of European and international experiences. The total of 38 laboratories took part in "WATER ANALYSIS-2003". Three laboratories were from Greece, one from the Republic of Srpska - Bosnia and Hercegovina, eight from Romania and all others from Serbia and Montenegro. The task for participants was to determine some or all trace elements (Al, As, Cd, Cu, Mn, Fe, Pb and Zn) in two samples prepared from filtered water of the river Danube near Belgrade. Participants could freely select the analytical methods. Results obtained for the determination of lead and cadmium were presented in this paper. All results were analysed using the same methods as in the interlaboratory studies organized by IRMM-JRC (Institute for Reference Materials. and Measurements: EU-Joint Research Centre, Geel, Belgium) within IMEP (International Measurements Evaluation Programme). Reproducibility (R) and repeatability (r) were calculated according to the British standard BS 5497: Part 1: 1987 (ISO 5725: 1986). The interlaboratory study was successful and most of laboratories obtained good results. Their achievement was better than in some earlier interlaboratory studies.