In the assessment of human health risk, the obtainment of reference values in biological tissues and/or fluids is crucial to estimate the type and magnitude of occupational and environmental exposure. In this context, urine is the major excretion route for many noxious substances that have entered the organism and can be viewed as one of the most useful materials for biomonitoring campaigns. In this study, reference concentration ranges for Cr, Ni and V in urine were achieved in a sub-population of 131 youngsters, aged 6-10, attending primary schools in the urban area of Rome. Subjects under drug therapy or affected by any pathological diseases were not included in this investigation. Strict precautions against contamination or loss of the analytes of interest were adopted for all steps. Determinations were performed by means of high resolution inductively coupled plasma mass spectrometry. In general, the natural log-transformed concentration data for the three elements investigated conformed to a satisfactorily normal distribution. The estimated reference ranges were as follows (microg g(-1) creatinine): Cr, 0.07-0.76; Ni, 0.20-1.23; V, 0.02-0.22. The sex of the youngsters was tentatively treated as a statistical explanatory variable using the Fischer F-test on variance.