In patients who had not previously received methotrexate or therapeutic doses of methotrexate, tofacitinib monotherapy was superior to methotrexate in reducing signs and symptoms of rheumatoid arthritis and inhibiting the progression of structural joint damage. The benefits of tofacitinib need to be considered in the context of the risks of adverse events. (Funded by Pfizer; ORAL Start ClinicalTrials.gov number, NCT01039688.).