The carcinogenicity of vinyl halides is reviewed. Laboratory studies have demonstrated that inhalation exposures of vinyl chloride (75014), vinyl bromide (593602), and vinylidene chloride (75354) cause angiosarcoma of the liver, as well as other cancers in animals. Several investigators have reported that vinyl chloride is mutagenic. Studies on workers exposed to vinyl chloride have indicated an excessive risk of death from cancer of the lung, brain lymphatic system, and angiosarcoma of the liver. There have been no reported cases of cancers in humans associated with exposure to vinyl bromide or vinylidene chloride. A significant increase in the frequency of chromosomal aberrations in the lymphocytes of workers exposed to vinyl chloride has been reported; but no such increases have been associated with vinyl bromide and vinylidene chloride. Other reported health effects from exposure to vinyl chloride include headaches, dizziness, fatigue, weakness, and neurologic disturbances. OSHA has set an occupational exposure limit of 1 part per million to vinyl chloride. Both NIOSH and OSHA recommend that occupational exposure to vinyl bromide and vinylidene chloride be reduced to the lowest possible concentrations, in light of recent indications of their potential carcinogenicity.