OBJECTIVES: To describe the prevalence of comorbidities in the newly diagnosed mCRC population. METHODS: The study used a large US claims database. Patients aged ≥18 with newly diagnosed mCRC between January 2005 and June 2008 were selected using the ICD-9 diagnosis codes (CRC: 153.x [excluding 153.5], 154.0, 154.1, 154.8; distant metastasis: 196.0, 196.1, 196.3, 196.5, 197.x (excluding 197.5), 198, 199.0). The initial mCRC diagnosis date was defined as the index date. One-year continuous medical and drug benefit coverage prior to the index date was required. Medical diagnoses and medication treatments were examined. All comorbidities were estimated during 1-year except for traumatic conditions which were assessed for 30-day prior to the index date. RESULTS: Based on the selection criteria, 12,648 patients were included with mean (±standard deviation) age of 66.3 (±13.0) years, 54% male, and 70% with colon primary. Distribution of metastases included liver (40%), lung (14%), bone (6%), and brain (3%). The most prevalent comorbidity was cardiovascular disease (CVD) (62% of patients) including hypertension (41%), coronary artery disease (17%), congestive heart failure (7%), dysrhythmias (14%), arterial thromboembolism including ischemic heart disease (18.6%), and venous thromboembolism (6%). Over 10% of patients had a major surgery, bone fracture, or open wound 30 days prior to mCRC diagnosis; 31% had a history of bleeding; and nearly 12% of patients were treated with anticoagulant and 6% with antiplatelet agents. Additionally, 19% of patients had diabetes, 8% had renal failure or insufficiency, and 5% had skin disorders. Patients ≥ 65 years old had a significantly higher CVD prevalence (73%; p<0.001). CONCLUSIONS: Comorbid medical conditions are common in patients with mCRC. CVD is the most prevalent comorbidity and affects approximately ¾ of patients over age 65. It is important to assess comorbidities in all patients with mCRC since their presence may impact treatment decision making.