Gram IT, et al. - Researchers examined if the heightened risk of colorectal cancer due to cigarette smoking varied by anatomical subsite and gender. The Multiethnic Cohort Study conducted in 1993-1996 yielded data from 188,052 participants (45% men, aged 45-75 years) for this work. The development of invasive colorectal adenocarcinoma was reported in 4,879 cases during a mean follow-up of 16.7 years. Multivariate Cox regression models revealed that relative to never smokers of the same gender, male ever smokers exhibit a 39% higher risk of left, but not of right colon cancer, while female ever smokers exhibit a 20% higher risk of right, but not of left colon cancer. A greater increase in the risk of rectal cancer was observed with the number of pack-years among female smokers vs male smokers.