The risk of mortality from lung cancer or asbestosis was assessed in a cohort of workers who had been exposed to chrysotile (12001295). Data were taken from a NIOSH cohort mortality study of employees at an asbestos textile factory in South Carolina in which only chrysotile was used as the raw fiber. The cohort consisted of 3,037 employees (1,793 males) employed at the facility for at least 1 month between 1 January 1940 and 31 December 1975 and followed up until the end of 1990. Associations between cumulative asbestos exposure and lung cancer and asbestosis mortality were examined by multiplicative and additive models using log linear, log quadratic, additive relative rate, power, and threshold parametric functions using Poisson regression techniques. Cumulative excess lifetime risks of dying from lung cancer and from asbestosis were estimated for the white males in the cohort (total of 1,247) using an actuarial method originally developed for assessing risks associated with radon exposures. The best fit to the lung cancer data was obtained with a log linear expression on a multiplicative scale which expressed the predicted incidence rate as the product of cumulative asbestos exposure and the background lung cancer incidence rate. The background lung cancer incidence rate was itself a function of age, sex, race, and calendar time. The best exposure response relation for asbestosis was nonlinear, also expressed on the multiplicative scale. No evidence of a threshold effect was seen for either lung cancer or asbestosis. The excess lifetime risk for 45 years exposure at the current OSHA standard, 0.1 fiber per milliliter, was estimated to be 5/1,000 for lung cancer and 2/1,000 for asbestosis. The authors conclude that a strong exposure response relationship exists between occupational exposure to chrysotile, and lung cancer and asbestosis mortality. The estimated lifetime risk of lung cancer mortality is higher than those obtained in other chrysotile exposed populations. Possible reasons for the discrepant findings were discussed.