This study was set up to investigate potential chronic health effects associated with molding in the foundry industry. For this purpose, a cohort of 632 male molders was followed through 10 years with regard to cause-specific mortality. Comparisons were made with another cohort of skilled workers. The mortality from cancer was increased among the molders (standardized mortality ratio 152, 95% confidence interval 100-221), mainly because of an excess number of deaths from bladder cancer (standardized mortality ratio 896, 95% confidence interval 329-1,949). It is suggested that certain mold types may emit bladder carcinogens. In addition, phenols, cresols, and aldehydes in the foundry work atmosphere might act as tumor promoters.