The possible association of colorectal adenomatous polyps, a precursor lesion for colorectal cancer, with cigarette smoking, alcohol consumption, and coffee and caffeine consumption was investigated in a case-control study. Between April 1986 and March 1988, 271 cases of patients with pathologically confirmed incident colorectal adenomatous polyps and 457 control subjects were collected from three colonoscopy practices in New York City. Information on exposure was obtained by structured interviews. After adjustment of age, statistically significant odds ratios (highest-lowest quartile) were found for cigarette smoking in males (2.2; 95% confidence interval (CI), 1.2 to 3.8) and coffee consumption in females (2.0%; 95% CI, 1.0 to 3.9). No significant associations were obtained for cigarette smoking in females, for coffee consumption in males, or for alcohol or caffeine consumption. After adjustments for alcohol, coffee, and caffeine consumption, the association of adenomas with cigarette smoking remained in males and significant associations were also observed in subcategory analysis for both left-side and right-side adenomatous polyps. Adjustment for cigarette smoking eliminated the association between colorectal adenomatous polyps and coffee consumption in females. Cigarette smoking appears to be a significant risk factor for colorectal adenomatous polyps in males.