BACKGROUND: Several studies have reported inverse associations between folate intake and colorectal carcinoma risk. Few were prospective studies and none evaluated the association between the intake of individual folate vitamers and colorectal carcinoma risk. METHODS: The aim of the current study was to investigate the relationship between dietary folate intake and the risk of colorectal carcinoma in a large prospective cohort study in The Netherlands comprising 120,852 men and women aged 55-69 years. After 7.3 years of follow-up, 760 colon and 411 rectal carcinoma cases were available for analysis. Data processing and analysis used the case-cohort approach. A new Dutch database was used to estimate intakes of total and individual folate vitamers. RESULTS: Analyses adjusted for age, energy intake, family history of colorectal carcinoma, alcohol, vitamin C, iron, and dietary fiber intake yielded an inverse association between colon carcinoma risk and total dietary folate intake (rate ratio [RR]highest vs. lowest quintile, men: 0.73; 95% confidence interval [CI], 0.46-1.17, P trend = 0.03; women: 0.68; 95% CI, 0.39-1.20, P trend = 0.18). An inverse association between rectal carcinoma and total dietary folate intake was found only among men (RR highest vs. lowest quintile, men: 0.66; 95% CI, 0.35-1.21, P trend = 0.03). Analyses showed no clear difference in colorectal carcinoma risk associated with intake of different folate vitamers. CONCLUSIONS: Dietary folate intake was related inversely to colon and male rectal carcinoma risk. Copyright 2002 American Cancer Society.DOI 10.1002/cncr.10866