A specially designed high resolution ICP-MS was combined with an ultrasonic nebulizer to analyze trace amounts of various inorganic contaminants contained in water samples. It was confirmed that the detection limits of most elements obtained by the proposed method were well under 1 ppt. The Standard Reference Material 1643b (trace elements in water) provided by NIST (National Institute of Standards and Technology, formerly U. S. National Bureau of Standards) was also analyzed. Concentration values obtained by this work were in good agreement with certified values for all the elements examined except for Cu. It can be concluded from the foregoing that the combination of the above two instruments materializes an extraordinarily sensitive method and paves the way for direct determination of a considerable number of trace and ultra-trace elements in water samples with acceptable speed and accuracy.