This testimony before the Subcommittee on the Environment concerned epidemiological studies dealing with the effects of vinyl-chloride (75014) exposures in the workplace. This substance has been shown to induce toxic effects including hepatic damage and acro osteolysis. On discovering its association with angiosarcoma of the liver, NIOSH met with other agencies having health research responsibility on February 1, 1974. Four working groups were formed: epidemiology, toxicology, industrial hygiene, and analytical methods, to draft plans to address this issue. A selection was made of facilities to be investigated in the epidemiologic aspect of this study, with the criteria being that the facility had been engaged in the polymerization of vinyl-chloride for at least 15 years, that it had a sizable work force, that it was located in a state with an ability to facilitate vital status ascertainment, and that it had an inhouse medical program. During the period from 1950 to 1973, a total of 109 deaths were observed among the vinyl-chloride polymerization workers; 105 would have been expected. The only disease category in which the deaths noted exceeded those expected was in the cancer deaths, a 57 percent increase over that expected. A NIOSH/CDC Surveillance Network has been established for identifying cases of angiosarcoma of the liver in vinyl-chloride polymerization workers. Statistics were provided with the testimony.