The possible association of colorectal adenomatous polyps, a precursor lesion for colorectal cancer, with risk factors including cigarette smoking, alcohol consumption, coffee consumption, family history and dietary factors was investigated in a case-control study. Between January 1993 and March 1995, 143 cases of patients with pathologically confirmed incident colorectal adenomatous polyps and 301 control subjects were collected from Our Lady of Mercy Hospital. Information on exposure was obtained by structured interviews. After adjustment for age and sex, statistically significant odds ratio (highest-lowest tercile) were found for cigarette smoking(5.53; 95% confidence interval CI, 3.26 9.38), coffee consumption (2.01 ; 95% CI 1. 15-3.53). For dietary factors, significant odds ratio were found for yogurt consumption (0.35 ; 95% CI 0.14-0.85) and milk consumption (0.34; 95% CI 0.17-0.70). No significant associations were observed for total fat intake and total fiber intake after adjustment for age, sex and total calorie. Odds ratio of family history of colorectal cancer and/or polyp was 3.05(95% CI 0.84-11.05). Cigarette smoking, coffee consumption, appears to be a significant risk factor, and milk consumption, yogurt consumption appears to be a significant protective factor for colorectal adenomatous polyps.