Mortality from colon cancer could be reduced with routine screening, yet screening rates are low. Current screening tools are limited by expense and suboptimal acceptance. A retrospective case-control study of all cases of colon cancer diagnosed at our institution over a 5-year period was performed to determine the frequency of blood count abnormalities in these patients upon presentation. One hundred twenty-seven patients had right-sided colon cancer: 107 (84%) had an elevated red cell distribution width (RDW); 87 (69%) had anemia; and 70 (55%) had a low mean corpuscular volume (MCV). Ninety-eight patients had left-sided colon cancer: 49 (50%) had an elevated red cell distribution width; 43 (44%) had anemia; and 22 (22%) had a low mean corpuscular volume. The red cell distribution width was 84% sensitive and 88% specific for right-sided colon cancer. An elevated red cell distribution width may help better identify those patients who should be referred for full colonoscopy.