3603 Background: Cancer patients are at increased risk of venous thromboembolism (VTE). VTE risk varies with cancer treatments and patient clinical and sociodemographic characteristics, including age. Methods: Patients older than 65 diagnosed with stage III or IV colon cancer (CC) during 2004 or 2005 within the linked Surveillance, Epidemiology, and End Results (SEER)-Medicare database were included. Patients were excluded if they participated in a managed care Medicare plan since administrative claims data from managed care plans are incomplete. Crude rates of VTE during the year following diagnosis by various demographic, clinical and treatment patient characteristics were calculated. Factors associated with VTE incidence were explored in adjusted analyses for the patients without chemotherapy and patients with chemotherapy that preceded VTE. Results: Crude rates of VTE during the year after CC diagnosis were 13.8% across all patients, 17.1% for African Americans, 13.8% for non-Hispanic Whites, 12.8% for Hispanics, and 7.7% for other racial/ethnic groups. VTE rates were 13.2% and 14.7% for stages 3 and 4, respectively. VTE was more common among patients with a VTE during the 12 months before CC diagnosis (38.2%) and those who received any chemotherapy (14.1%), biologics (22.6%) or newer chemotherapy (e.g., irinotecan or oxaliplatin) with or without biologics (16.2%) as compared to a 5FU/L-based regimen. Multivariable logistic regression results confirmed the impact of prior VTE (OR 4.27, 95% CI 3.38-5.39), African American race (OR 1.25, 95% CI 1.02-1.53), and receipt of newer chemo agents and biologics (OR 1.28, 95% CI 1.08-1.52) on increased risk of VTE. Conclusions: Approximately 1 out of every 7 elderly Americans with stage III or IV colon cancer has a VTE diagnosis within the first year following diagnosis. The odds of VTE are impacted by prior VTEs, treatment-related variables, such as chemotherapy and use of biologic agents and demographic characteristics such as African-American race. These results suggest that there is a need to incorporate appropriate VTE prophylaxis regimens into treatment guidelines for these patients to minimize the incidence and sequelae. Author Disclosure Employment or Leadership Position Consultant or Advisory Role Stock Ownership Honoraria Research Funding Expert Testimony Other Remuneration sanofi-aventis Amgen, Bayer, Bristol-Myers Squibb, Genentech, GlaxoSmithKline, Lilly, Merck, Novartis, Pfizer, sanofi-aventis sanofi-aventis Pfizer, sanofi-aventis GlaxoSmithKline, Novartis, Pfizer, sanofi-aventis