We report a case of signet cell carcinoma of the colon in a patient with Crohn's disease. Signet cell carcinoma, also termed linitis plastica, is an unusual malignancy of the colon and is rarely associated with Crohn's disease. In general, metastatic disease is evident at the time of diagnosis, and the prognosis is uniformly poor. The radiographic, endoscopic, and histological features are discussed.