Cor pulmonale has been reported in the past to be associated with pneumoconiosis as an end-stage complication. However, whether the association can be demonstrated among cases of pneumoconiosis acquired in more recent decades is not clear. We examined the relation between these conditions using data summarized in hospital records in Ontario for males discharged between 1979 and 1990 with a diagnosis of chronic cor pulmonale or one of the pneumoconioses. Based on the age-specific frequency rates, cor pulmonale was diagnosed 17 (95% confidence interval 13-22) times more frequently than expected among men diagnosed with pneumoconiosis than among other men admitted to hospital. Our investigation indicates that cor pulmonale still appears to be associated with dust exposure in the workplace, and it demonstrates the usefulness of hospital discharge information in addressing questions in occupational health. However, we recommend that hospital medical records be examined to confirm the diagnoses and to determine the smoking histories of these men.