This study aims to reconfirm the clinical efficacy and related factors of infliximab therapy, the first biological agent introduced to Japanese patients with rheumatoid arthritis (RA). Data of 351 RA patients with infliximab were collected retrospectively from three major centers for management of rheumatic diseases in Japan. Infliximab was infused according to the approved method, and the clinical response was evaluated following 22 weeks of infliximab therapy in 258 patients using the European League Against Rheumatism (EULAR) response criteria. DAS28-CRP (Disease Activity Score including a 28-joint count/C-reactive protein) with a threshold of 4.1 or 2.7 for the high or low disease activity cut-off was also used. A total of 90.3% of patients exhibited high disease activity before infliximab therapy. After 22 weeks of infliximab therapy, the proportions of patients exhibiting high activity, moderate activity, low activity, or in clinical remission were 27.9%, 33.3%, 10.9%, or 27.9%, respectively, thereby indicating good overall efficacy of infliximab therapy. A good or moderate overall response to therapy was achieved in 84.5% of patients. Male sex, rheumatoid factor (RF) negativity, low CRP, lower swollen joint count and a low prednisolone dose were significantly related to the clinical response. Furthermore, male sex, older age, and a high tender joint count had a significant correlation with treatment discontinuation as a result of adverse reactions. In conclusion, we have reconfirmed the effectiveness of infliximab in Japanese patients with RA by using DAS28-CRP and EULAR response criteria. These data will facilitate more efficacious use of this expensive biological agent in the daily practice of rheumatology in Japan.