A simple flow injection on-line dilution procedure with detection by inductively coupled plasma mass spectrometry (ICP-MS) was developed for the determination of copper, zinc, arsenic, lead, selenium, nickel and molybdenum in human urine. Matrix effects were minimized by employing a dilution factor of 16.5 with on-line standard addition, and Rh-103 was used as internal standard to compensate for signal fluctuation. The procedure was validated by the analysis of two standard reference materials SRM 2670 (NIST) and Seronorm (TM) Trace Elements in Urine. Recovery experiments were pet-formed by spiking the reference materials as well as artificial urine. The detection limits (mug l(-1)) were 0.12, 0.96, 0.30, 0.09, 0.45, 0.08, 0.09, and the precisions (RSD,%) were 2.6, 2.3, 3.0, 3.7, 3.7, 4.9, 2.8 for Cu, Zn, As, Pb, Se, Ni and Mo, respectively. The procedure was applied to the analysis of 41 human urine samples. No correlations between the concentrations of the elements were observed. (C) 2001 Elsevier Science B.V. All rights reserved