The National Institute for Occupational Safety and Health (NIOSH) has received a report from an American producer of hexamethylphosphoric triamide (HMPA), a synthetic organic chemical, indicating that malignant tumors have been produced in laboratory animals by exposure to HMPA. In light of the potential risk of human exposure to this chemical in the work environment, the National Institute for Occupational Safety and Health is advising the occupational health community of these findings. The occupational hazards presented by hexamethylphosphoric-triamide (680319), responsible for the induction of experimental nasal squamous cell carcinoma in rats, are reviewed briefly. It is estimated that 5,000 workers are occupationally exposed to the compound, most of them in research laboratories. There is no current OSHA standard for hexamethylphosphoric-triamide exposure.