Analyses of radiographs from a cohort of 457 school maintenance and custodial workers (90 had no employment other than at a school) demonstrated an increased prevalence of abnormalities consistent with asbestos-caused disease. Pleural abnormalities predominated (24 of 29). The abnormalities could not be explained by occupational asbestos exposures which may have occurred prior to school employment. Abnormality prevalence ranged from 1.7% among those with less than 10 years to 37% among those with 30 or more years of public school employment. Laborers and skilled tradesmen with more than 20 years of school employment had a higher prevalence of abnormality (40 and 28%) than the building engineers (14%). In order to ensure that future asbestos exposure and disease risk is minimized in buildings constructed with asbestos-containing materials (ACM), implementation of asbestos hazard identification and abatement must include a rigorous operations and maintenance program. Control of asbestos exposure from in-place ACM is a public health priority.