In a prospective cohort study of 3893 shipyard workers, we estimated the value of medical monitoring, including chest radiograph, spirometry, and questions about smoking habits, asbestos exposure, and respiratory symptoms, as predictors of the risk of developing mesothelioma. There was no strong association between different exposure parametersand risk of mesothelioma. Impaired lung function and smoking were not predictors of risk of mesothelioma. Pleural plaque was not found to be associated with an increased risk of mesothelioma. Respiratory symptoms were of low value as predictors of risk of mesothelioma. Thus, traditional methods in health monitoring seem to be of low value in identifying persons with a high risk of mesothelioma in populations exposed to asbestos.