This study was one of two 24-week, phase 2b studies undertaken to characterise the efficacy and safety dose-response profile of the oral Janus kinase (JAK) inhibitor tofacitinib. Six doses of tofacitinib (20 mg daily and 1, 3, 5, 10 and 15 mg twice daily) and placebo were compared as add-on therapy in adults with active RA despite methotrexate (MTX) therapy. At week 12, ACR 20 response rates were significantly higher with all tofacitinib doses than with placebo (tofacitinib 45.7–58.1%; 33% place...