Four adults, including a pregnant woman, and three children were admitted to hospital following accidental exposure to mercury vapour produced by heating mercury-gold amalgam. Initial symptoms and signs included a paroxysmal cough, dyspnea, chest pain, tachypnea, nausea, vomiting, fever and leukocytosis. Pulmonary function testing performed on the second day after exposure revealed air-flow obstruction and minor restrictive defects in three patients. The diffusing capacity of the lung for carbon monoxide was reduced in two of these patients. The mean initial blood mercury level (+/- one standard deviation) for the seven patients was 30.8 +/- 1.5 micrograms/dl. A computer analysis showed mercury to behave as a two-compartment system, the compartments having half-lives of 2 and 8 days. The four adults received chelation therapy with D-penicillamine, which did not affect the urinary excretion of mercury. The pregnant woman's infant, born 26 days after exposure, had no detectable clinical abnormalities. The levels of mercury in the blood of the mother and infant at birth and 6 days later were comparable, indicating free transfer of the metal across the placenta.