This 1983 to 1985 update of an earlier study examined the mortality experience of 16,661 man-made mineral fiber workers employed 1 year or more (6 months for two plants) during 1945 to 1963 (1940 to 1963 for one plant) at one or more of 17 US manufacturing plants. Using local death rates to estimate expected deaths there was a small statistically significant (P less than .05) excess in all malignant neoplasms (standardized mortality ratio [SMR] = 108.3) and in respiratory cancer (SMR = 112.1) for the total period 1946 to 1985. For respiratory cancer the excess was greatest for mineral wool workers. For glass wool workers and glass filament workers respiratory cancer SMR values were much lower. For workers exposed in the production of small-diameter fibers, the overall respiratory cancer SMR was slightly elevated but lower than in earlier reports. A total of four malignant mesotheliomas have now been noted on death certificates. Two of these were coded to the International Classification of Disease rubrics used to estimate 1.45 expected mesothelioma deaths for the total study. Overall, the evidence of a relationship between exposure to man-made mineral fibers and respiratory cancer appears to be somewhat weaker than in the previous update.