A proportionate mortality ratio (PMR) study was undertaken of 7,121 members and retirees of the United Association of Plumbers and Pipefitters in California who died in 1960-79. The PMR for all malignant neoplasms was 1.24, with a major contribution from lung cancers (PMR = 1.41). Lung cancer PMRs were consistently elevated, through the 20-year study period, across the pipe trades and within different birth cohorts. Sixteen mesothelioma deaths occurred, suggesting asbestos as a risk factor. PMRs for malignancies of the stomach, kidney, brain, and lymphopoietic system were also elevated, especially among plumbers. Chronic rheumatic heart disease, emphysema, liver cirrhosis, and all external causes of death were the major non-cancer causes with significantly elevated PMRs. There were significant deficits in diabetes mellitus, all pneumonia, chronic nephritis, and vascular lesions of the central nervous system (CNS). PMRs for successive birth cohorts among all study subjects revealed decreasing emphysema risk, suggesting previous reduction of a risk factor for this disease. Among plumbers, PMRs for death due to several non-respiratory malignancies showed an increasing trend with recency of birth cohort.