The determinants of radiographic worsening were examined in a cohort of 244 asbestos-cement manufacturing workers. Progression of irregular small opacities was related to higher average and cumulative dust exposures. Progression of pleural thickening or pleural plaques was related to length of exposure and time since first exposure, but not to average or cumulative exposure. Larger declines in forced vital capacity and forced expiratory volume (one second) were related to larger cumulative dust exposures and to progression of irregular small opacities and pleural thickening. Progression of pleural calcification was not associated with significantly declines in lung function. Changes in lung diffusing capacity did not correlate with measures of dust exposure or with progression of radiographic abnormalities.