The role of occupational substances as stomach carcinogens has not been well investigated. In 1979, a population-based case-control study was undertaken in Montreal to explore the possible association between hundreds of occupational circumstances and several cancer sites, including the stomach. In total, 250 male patients with pathologically confirmed stomach cancer, 2,289 male controls with cancers at other sites, and 533 population-based male controls were interviewed to obtain detailed job histories and relevant data on potential confounders. Job histories were evaluated by expert chemists and hygienists and translated into a history of occupational exposures. On the basis of results of preliminary analyses and literature review, we selected 16 occupations and industries and 32 substances for in-depth multivariate analysis using the pooled group of cancer and population controls. We found elevated risks for excavators and pavers, forestry workers, electric and electronic workers, motor transport workers, and food industry employees. The substances that were most plausibly associated with gastric cancer were: crystalline silica, leaded gasoline, grain dust, lead dust, zinc dust, hydraulic fluids, and glycol ethers. The paucity of data documenting the association between most of these occupational circumstances and gastric cancer precludes drawing firm conclusions.