Unusual infections associated with colorectal tumors may, in some instances, be the sole clue to the presence of a malignancy. The infections are either related to invasion of tissues or organs in close proximity to the tumor or secondary to distant seeding by transient bacteremia arising from necrotic tumors. Seven patients seen at one hospital over a 5-year period illustrate the clinical presentations of such infections. The infections identified in these seven patients include endocarditis, meningitis, nontraumatic gas gangrene, empyema, hepatic abscesses, retroperitoneal abscess, clostridial sepsis, and colovesical fistulae with urosepsis. A computer-assisted search of the English-language literature and cross-checks from other review articles identified other infections associated with colon cancer, which include nontraumatic crepitant cellulitis, suppurative thyroiditis, pericarditis, appendicitis, pulmonary microabscesses, septic arthritis, and fever of unknown origin. The clinical importance of these infections and their correlation with colorectal malignancies are reviewed.