ABSTRACT. Objective. To assess the effectiveness of rituximab (RTX) in patients with rheumatoid arthritis (RA) in routine clinical practice, and to identify predictors of 6-month response to RTX in patients for whom at least 1 anti-tumor necrosis factor-α (anti-TNF) therapy has failed. Method. The analysis involved 646 patients with RA registered with the British Society for Rheumatology Biologics Register (BSRBR) who were starting RTX and were followed for at least 6 months. Change in the 28-joint Disease Activity Score (DAS28), European League Against Rheumatism (EULAR) response, and proportions of patients achieving disease remission were used to assess the clinical response 6 months after starting RTX. Regression analyses were used to identify factors associated with the response in the patients for whom anti-TNF therapy had not worked. The models included baseline demographics, disease characteristics, baseline Health Assessment Questionnaire (HAQ), and drug history including biologic history.Results. The mean DAS28 at baseline was 6.2 (95% CI 6.1, 6.3), which decreased significantly to 4.8 (95% CI 4.7, 4.9) at the 6-month followup. Seventeen percent of the patients were EULAR good responders and 43% were moderate responders. Eight percent of the patients achieved disease remission. Subjects with higher baseline DAS28 score and those with positive rheumatoid factor (RF) status were significantly associated with a decrease in their DAS28 score (improvement), while women and patients with higher baseline HAQ score were less likely to improve. Conclusion. RTX has proven to be effective in routine clinical practice. When anti-TNF therapy fails, response to RTX was influenced by baseline DAS28 score, RF status, baseline HAQ score, and sex.