OBJECTIVE: To evaluate the seroprevalence of hepatitis B (HBV) and C (HCV) in patients living in France with recent-onset polyarthritis suggesting rheumatoid arthritis. METHODS: The 813 patients in the ESPOIR cohort were screened for anti-HCV antibodies and HBs antigen. RESULTS: Seroprevalence was 0.86% for HCV (n = 7) and 0.12% for HBV (n = 1). HCV-related arthritis was diagnosed in 4 (0.5%) patients; no patient had HBV-related arthritis. HCV-seropositive patients had significantly higher transaminase levels (ALAT, 41.5 IU vs 23.2 IU, p = 0.02; and ASAT, 39.2 IU vs 21.8 IU, p = 0.001) but only 2 patients had ASAT or ALAT levels > 40 IU. No significant differences were found for anti-CCP antibodies, C-reactive protein, erythrocyte sedimentation rate, or other test. HCV seroprevalence was significantly higher in the subgroup with history of blood transfusion than in other patients (3.7% vs 0.42%, p = 0.02). Two of the 7 HCV positive patients and the single patient with confirmed hepatitis B infection were born in areas with higher prevalence of viral hepatitis (Togo, Senegal, Vietnam). Positive hepatitis status was known before study inclusion in 4 of the 7 HCV-positive patients and in the HBV-positive patient. CONCLUSION: The prevalence of HBV and HCV in a population of patients with recent-onset polyarthritis suggestive of RA was not greater than expected based on data from the general population in the same geographic area. Routine HBV and HCV serological testing did not contribute substantially to the diagnosis of recent-onset polyarthritis. Although advisable before initiating immunosuppressive or hepatotoxic drugs, serological testing for HCV and HBV is unnecessary in routine diagnostic evaluation of recent-onset polyarthritis.