OBJECTIVE To estimate the prevalence of low hemoglobin (Hb) levels in a large US cohort of patients with rheumatoid arthritis (RA) and examine the relationship between Hb levels and RA severity, associated comorbidities, and quality-of-life parameters by cross-sectional analysis of data from the Consortium of Rheumatology Researchers of North America (CORRONA) registry. METHODS The study population comprised patients with RA >18 years of age and clinical information recorded in the CORRONA registry between October 1, 2001 and February 1, 2007. Patients were separated into low (Hb <13 g/dl for men; <12 g/dl for women) and normal Hb groups (Hb >13 g/dl for men; >12 g/dl for women). Hb levels were calculated from recorded hematocrit values. RESULTS Of the 10,397 study patients, 1734 (16.7%) had low Hb levels and 8663 (83.3%) had normal Hb levels. More patients in the low Hb group had a history of comorbid cardiovascular disease, diabetes, and gastrointestinal disease. The low Hb group exhibited greater disease severity and activity (p<0.05) as reported by patients and rheumatologists. In multivariate analyses, RA severity ([odds ratio] OR 1.24; 95% confidence interval [CI]: 1.07-1.44) and ESR (OR 1.04; 95% CI: 1.03-1.05), and comorbid bleeding ulcers (OR 2.04; 95% CI: 1.01-4.12) were predictive of low Hb levels. CONCLUSION Despite changes in treatment paradigms, low Hb levels remain prevalent in RA patients. This analysis suggests that low Hb levels may be associated with RA disease severity and the presence of certain comorbidities.