Similarities exist in the epidemiology and immunopathogenesis of periodontitis and rheumatoid arthritis (RA), but the associations between their respective disease activities and severities are less well documented. We evaluated the prevalence and severity of periodontitis in United States (U.S.) veterans with RA and their relationship to RA disease activity and severity. Patients with RA from an outpatient rheumatology clinic were eligible, and patients with osteoarthritis (OA) served as controls. Dentists, masked to the rheumatologic diagnoses, performed periodontal probing and examined dental panoramic radiographs to assess the presence and severity of periodontitis. Associations of periodontitis with RA were examined using multivariate regression, whereas the association of periodontitis with disease-severity measures in RA was examined using the chi(2) test. Sixty-nine patients with RA (57 males and 12 females) and 35 patients with OA (30 males and five females) were studied. Moderate to severe periodontitis was more prevalent in patients with RA (51%) than controls (26%) (P = 0.03), an association independent of age, race, smoking, diabetes mellitus, and gender. Patients with RA who were seropositive for rheumatoid factor (RF) were more likely to have moderate to severe periodontitis (59%) than patients who were RF negative (15%) (P = 0.02). Likewise, patients with RA who were positive for the anti-cyclic citrullinated peptide (CCP) antibodies were more likely to have moderate to severe periodontitis (56%) than patients who were anti-CCP negative (22%) (P = 0.01). There were no associations of periodontitis status with other measures of RA disease activity or severity. In a cohort of U.S. veterans, periodontitis was more common and severe in patients with RA compared to patients with OA. Although unrelated to disease activity, the presence of periodontitis in patients with RA was associated with seropositivity for RF and the anti-CCP antibody, which was highly relevant given the associations of these autoantibodies with poor outcomes and disease pathogenesis in RA.