The increased industrial use of platinum has led to a growing need for the determination of platinum levels in biological materials. Concern about the release of toxic material from catalytic converters in motor vehicles in the environment and about occupational platinum exposure of employees working in the assembly of motor vehicle catalyzers and recycling led us to establish background and internal exposure levels in human body fluids. The development of an analytical procedure, based on adsorptive voltammetry with an extremely high power of detection (2 pg Pt absolute) for the determination in body fluids made population studies reliable and practicable. The methods are described and the reliability criteria are presented. For 13 not occupationally exposed persons the platinum levels ranged in urine from <EQ 0,4 - 14,3 ng/l, in whole blood from <EQ 0,8 - 6,9 ng/l and in plasma from <EQ 0,8 - 6,9 ng/l. Employees (N equals 40) engaged in various workplaces with the manufacturing and recycling of platinum containing catalysts showed much higher platinum levels ranging from 10 - 2900 ng/l urine, 2 - 180 ng/l blood and 4 - 280 ng/l plasma. This was in agreement with the external exposure levels, which exceeded the German MAK value of 2 (mu) g/m3. Platinum concentrations in human biological materials seem to be suitable as internal exposure indicators.