We investigated the association between plasma 25( OH) D and the subsequent colorectal cancer incidence risk by a nested case control study in The Japan Public Health Center- based Prospective Study, covering 375 newly diagnosed cases of colorectal cancer from 38 373 study subjects during a 11.5- year follow- up after blood collection. Two controls were matched per case on sex, age, study area, date of blood draw, and fasting time. In a conditional logistic regression model with matched pairs adjusted for smoking, alcohol consumption, body mass index, physical exercise, vitamin supplement use, and family history of colorectal cancer, plasma 25( OH) D was not significantly associated with colorectal cancer in men or in women. However, the lowest category of plasma 25( OH) D was associated with an elevated risk of rectal cancer in both men ( odds ratio ( OR), 4.6; 95% confidence interval ( CI), 1.0 20) and women ( OR, 2.7, 95% CI, 0.94 - 7.6), compared with the combined category of the other quartiles. Our results suggest that a low level of plasma 25( OH) D may increase the risk of rectal cancer.