Three siblings with inhaled elemental mercury toxicity are described, and the signs and symptoms of mercury toxicity, interpretation of mercury concentrations, and management of elemental mercury exposure are reviewed. A 4-year-old girl was admitted to the hospital with a history of fever and increasing irritability, fatigue, malaise, insomnia, headache, anorexia, and ataxia. She was discharged two days later with a diagnosis of acute cerebellar ataxia. During the following 18 days, the child's condition worsened, and she was rehospitalized. Meanwhile her 11-year-old sister was hospitalized for evaluation of fatigue, weakness, lower back pain, and ataxia. The older girl's blood mercury concentration, at 5.5 micrograms/dL, was in the toxic range. Twenty-four-hour urine mercury screening confirmed mercury intoxication in both children. Questioning revealed that the girls' brother had recently spilled 0.5-1 oz of elemental mercury in the house. All family members underwent blood and urine mercury testing. The brother underwent a dimercaprol challenge to determine his tissue mercury burden, which was found to be greater than 2.4 micrograms/dL. The sisters underwent two courses of chelation therapy with dimercaprol. Symptoms persisted in all three children, and they underwent five 10-day cycles of N-acetyl-D,L-penicillamine (NAP) therapy; the youngest underwent a third dimercaprol regimen. All siblings continued NAP chelation therapy because of extensive tissue mercury burden until the results of repeated urine mercury concentration determinations were normal.(ABSTRACT TRUNCATED AT 250 WORDS)