A systematic study was carried out on the effect of ICP-MS operational parameters, such as dwell time, sweeps per reading, readings per replicate and number of replicates, on the precision and accuracy of results obtained in the semiquantitative mode by using Rh as internal standard and Ge, In and Ri for internal calibration of the instrument. In order to improve the quantitative analysis of major elements, such as Na, Mg, K and Ca, the detector attenuation (OmniRange parameter) must be recalibrated by using a multi-standard solution of these elements, Under these conditions, accurate results were obtained with a total measurement time of 103 s per sample, covering the whole mass range from 6 to 238 mu. The applicability of the methodology developed was confirmed by the analysis of a drinking water certified reference material.