The results of an industrial hygiene survey of heavy metal exposures at a smelter in Oruro, Bolivia were summarized. The survey was conducted in March 1994 by NIOSH, Bolivian public health personnel, and the Pan American Health Organization because of concerns about hazardous metal exposures, particularly to arsenic (7440382) and lead (7439921), at the smelter. Breathing zone samples were collected and analyzed for arsenic, lead, antimony (7440360), bismuth (7440699), cadmium (7440439), iron (7439896), tin (7440315), and zinc (7440666). Hazardous exposures to arsenic, cadmium, lead, and antimony were detected, the peak breathing zone concentrations being 390, 230, 280, and 4,500 micrograms per cubic meter (microg/m3), respectively. No overexposure to the other metals was detected. Sulfur-dioxide (7446095) exposures ranged up to 31 parts per million (ppm). Lead and arsenic concentrations as high as 5,210 and 7,342 microgram per gram (microg/g) were measured in settled dust samples collected throughout the facility. No significant accumulation of lead or arsenic in drinking water samples was detected. The blood lead and urine arsenic concentrations varied from 13 to 54microg per deciliter (microg/dl) and from below 1 to 260microg/g creatinine, respectively. The mean concentrations were 19ug/dl and 78microg/g. A review of the facility's respirator program found that the respirators provided were inadequate, and respirators in high exposure areas were not always consistently or properly used. The NIOSH investigators concluded that the smelter's program to control worker exposures to heavy metals and sulfur- dioxide was not adequate. Recommendations for reducing hazardous exposures at the facility include more thoroughly assessing occupational exposures to heavy metals and sulfur-dioxide, improving the respirator protection program, improving housekeeping practices, and implementing a medical surveillance program for the workers.