Although it has been hypothesized that carbon black exposure may carry an excess risk of lung cancer, evidence to date is insufficient to assess the hypothesis properly. The relationship between workplace exposure to carbon black and lung cancer risk was examined in a population-based case-control study carried out in Montreal, Canada. Detailed job histories were elicited from 857 incident cases with histologically confirmed lung cancer as well as from 1,360 cancer controls and 533 population controls. Job histories were evaluated by a team of hygienists and chemists for evidence of exposure to a host of occupational substances, including carbon black. Logistic regression analyses adjusting for smoking and other nonoccupational and occupational potential confounders suggested no significant increase in risk with relatively low exposure to carbon black. Some increase in risk for all lung cancers was apparent with relatively high exposure using cancer controls (OR = 2.17; 95% CI = 0.95-4.91) and population controls (OR = 1.52; 95% CI = 0.58-3.97). Individuals with relatively high exposure had a significantly greater risk of oat-cell carcinoma using either control series (OR = 5.05; 95% CI = 1.72-14.87 using cancer controls and OR = 4.82; 95% CI = 1.36-17.02 using population controls). These results provide some evidence for an association between exposure to carbon black and lung cancer.