A mortality study was conducted from 1967 to 1987 on workers exposed to asbestos (1332214). An historical perspective of the identification of asbestos as a hazardous substance was presented through examination of publications describing lung disease in exposed workers from 1924 to 1979. A mortality study had been conducted of 17,800 insulation workers followed from 1967 to 1976. The present report extended observation of surviving workers from this cohort through 1987. During the 20 year period, 4,951 of the workers died; the expected value of 3,453 was based on statistical calculations from age and year specific death rates for United States white males. Increased incidences of cancer of the lung, larynx, oropharynx, kidney, pancreas, gallbladder, and bile ducts were observed. Increased incidences were related to latency, with most of the increased risk occurring 25 or more years after the onset of asbestos exposure. No increases were seen with respect to cancer of the urinary bladder, prostate, testis, liver, or brain.