The United Association of Journeymen and Apprentices of the Plumbing and Pipefitting Industry was concerned about the numerous occupational hazards to which its members were exposed and therefore wanted to determine whether unusual mortality patterns could be identified among its membership. The National Institute for Occupational Safety and Health undertook a mortality analysis of the United Association's members and found significant excesses of cancer of the esophagus and of the respiratory and lymphatic systems among those in the plumbing trade. Although plumbers are potentially exposed to several known and suspected carcinogens, additional study is needed to further document the excesses and to determine whether these excesses can be related to specific occupational exposures.