A case of squamous cell carcinoma arising in a duplication of the colon is reported, and the literature of squamous cell carcinoma of the colon and of malignancy complicating duplications of the colon is reviewed. This is the 23rd case of "pure" squamous cell carcinoma of the colon to be reported, and the second reported as arising in a duplication of the colon. Several possible mechanisms for the development of a squamous cell carcinoma in the colon are discussed.