Occupational exposure to formaldehyde (50000) in kidney dialysis units was discussed. Formaldehyde is commonly used to sterilize kidney dialysis units. Epidemiological studies conducted by the National Institute for Occupational Safety and Health (NIOSH) were summarized. These have shown formaldehyde exposures up to 0.9 parts per million (ppm) and 1.9 milligrams per cubic meter occurring in dialysis units in hospitals in San Francisco, California, and Denver, Colorado, respectively. Employees at the San Francisco unit also reported experiencing cough, headache, and irritation of the eyes, nose, and throat. The physiological consequences of acute inhalational exposure to formaldehyde were described. These range from eye and upper respiratory tract irritation at exposures of 0.1 to 5ppm to pulmonary edema, pneumonitis, or death occurring at exposures of 50 to 100ppm. Formaldehyde induced dermatitis was discussed. Formaldehyde carcinogenicity was considered. Formaldehyde has been shown to induce a rare type of nasal cancer in Fischer-344-rats and B6C3F1-mice. It apparently causes the same type of cancer in Sprague-Dawley-rats. Based on these findings, NIOSH has recommended that formaldehyde be treated as a potential occupational carcinogen. Recommendations for minimizing exposure to formaldehyde in dialysis units were given. These included wearing appropriate protective clothing and equipment, ensuring that lines connecting portable and console units to the drain line be airtight, providing ventilation sufficient to achieve five air changes per hour in all rooms where formaldehyde is being used, and spending as little time as possible in rooms where dialysis units are being sterilized. NIOSH also recommends continually running water while sterilization is in progress in order to minimize formaldehyde vapors.