This study describes and evaluates the results of a round-robin wherein 22 lake water samples were submitted to eight private sector laboratories for application of their inductively coupled plasma emission spectrometry (ICP-ES) or mass spectrometry (ICP-MS) analytical packages. An objective of the project was to gain an appreciation for the quality of water analyses amongst production-oriented laboratories, and hence to use this information to assist in the design of sample collection and analytical programs in support of hydrogeochemical surveys. The 22 samples were in fact 11 duplicate pairs in order to provide data to facilitate an estimation of precision both within a laboratory and across laboratories; precision control charts were employed to this end. The accuracy observed for each element was more difficult to quantify, but was assessed by the degree of convergence of results using these independent analytical methods and techniques. The samples were spiked with varying amounts of Ba, Be, Cd, Co, Cu, Cr, Mn, Mo, Ni, Pb, V and Zn in order to raise their concentrations to levels above the detection capability of both techniques. The best estimate of precision (defined as twice the relative standard deviation) observed across the laboratories is: 10% for Mg, Mn, Na and Sr; 15% for Ba, Be, Ca, Cd, Co, Mo and V; 20% for As (ICP-MS only), Cu and Pb; 25% for Cr and K (ICP-ES only); 30% for Al and Sb (ICP-MS only); 35% for Zn; and 60% for Fe. Good precision was not necessarily a guide to good accuracy and the range in mean values for duplicates across laboratories was particularly wide for Al, B, Ca, Fe, K, Na and Zn. Most of the data from one laboratory had to be excluded from assessment of both precision and accuracy as their values deviated greatly from the average. A bias in absolute values between the two techniques was shown for Al only, ICP-MS yielding the lower results. Superior reproducibility was observed in the MS data for Al, Cr, Ni and Zn. The higher detection power of ICP-MS allowed the measurement of additional elements, namely As, Ce, Cs, I, La, Rb, Sb, Ti and U, to lower limits of 0.01 ppb.