Prior to the first infusion, patients will be randomized into one of two groups (placebo or infliximab). All patients will continue to receive the same does of methotrexate (MTX) during the study as received prior to the study. The objective of the study is to evaluate the efficacy and safety result of infliximab with Korean patients in reducing clinical signs and symptoms of rheumatoid arthritis (RA) at 30 weeks following the onset of treatment and to review whether the result is comparable to the result of the ATTRACT trial.