Urinary mercury levels were determined in 22 dentists and 46 dental nurses and assistants working in 15 private dental offices in West-Germany. For comparison, urinary mercury levels of 29 subjects without occupational mercury exposure were studied. On average, urinary mercury in dental personnel was higher than in the reference group. Individual mercury levels, however, were all significantly below present occupational exposure limits. Urinary mercury was significantly correlated with the number of amalgam fillings in dental personnel as well as in the reference group. Following administration of Dimaval a significant increase of mercury excretion was observed in both groups. Regarding total exposure to mercury in dental personnel, the contribution of mercury exposure from the occupational environment is of the same order of magnitude as their exposure from their own amalgam fillings. Dental nurses were found to be more exposed than dentists. This finding seems to be related predominantly to the larger number of amalgam fillings in dental nurses.