An extremely sensitive and reliable procedure for the determination of physiological (normal) Pt levels in human urine is described based on UV photolysis of the sample followed by the determination of Pt with magnetic sector field ICP-MS. Owing to the low blank values, which are a consequence of the minimal reagent addition required, UV photolysis was used to decompose the organic matrix components. Magnetic sector field ICP-MS operated in the low resolution mode afforded detection limits that were 100 times lower than those obtained in the high resolution mode or with conventional quadrupole ICP-MS and was found to be advantageous for the ultratrace determination of non-interfered isotopes. The detection limit in urine samples was 0.24 ng l^–1 using standard nickel cones. The use of a high performance nickel skimmer cone did not result in an improvement in the detection limit, because the analyte and background signals were enhanced to a similar extent. The urinary Pt levels in 16 non-exposed persons ranged between 0.48 and 7.65 ng l^–1(arithmetic mean: 1.72 ng l^–1).