OBJECTIVES:   RA is a systemic disease resulting in comorbidities that affect quality of life, prognosis and outcomes.  Comorbid illnesses can impact treatment, medical costs, disability and risk of mortality.  Rheumatoid Arthritis Outcomes Analyzer, a validated claims data analysis tool with a user-friendly interface was used to characterize comorbidities in patients with RA. METHODS:   The study included patients age 18 or older with at least 2 diagnoses of RA (ICD-9 CM 714.0X) ≥ 2 months apart between January 2005 and December 2007 from the HealthCore Integrated Research DatabaseSM.  Patients must have received ≥ one traditional (non-biologic) or biologic DMARD medication with RA diagnoses at least two months apart.  All medical and pharmacy claims were entered into the final dataset. RESULTS:   A total of 25,856 RA patients entered into the analysis (mean age = 56; 74.8% female).   The overall mean Charlson Comorbidity Index (CCI) was 2.00 (SD=1.63) and was higher for males (mean = 2.18; SD = 1.85) than females (mean = 1.94; SD = 1.55).  In the 18 to 44 age group, females tended to have a higher CCI (mean = 1.38; SD = 0.91) than males (mean = 1.30; SD = 0.81).  This trend reverses in older patients where the mean CCI in males in the 45 to 64 and ≥ 65 age groups is 1.90 (SD = 1.50) and 3.31 (SD = 2.39) respectively versus 1.76 (SD = 1.29) and 2.80 (SD = 2.07) in females.  The most frequent comorbid conditions for all patients were; chronic pulmonary disease, diabetes, cerebrovascular disease, tumor, congestive heart failure, peripheral vascular disease and renal disease. CONCLUSIONS: This analysis explores and differentiates the CCI by gender and age group in patients with RA using a validated claims data analysis tool.  Further study will examine the relationship between comorbidity and health-related and cost outcomes.