A number of over-sea study showed the immediate and dramatic anti-inflammatory effects of infliximab(IFX) in patients with rheumatoid arthritis (RA). In addition, significant reduction of bone/joint destruction by IFX was proven in RA patients. On the other hand, some serious adverse effects of IFX were documented. In Japan, IFX was approved as a biological reagent against RA on 2003, and nationwide post marketing surveillance was conducted in the consecutive 5,000 RA patients on IFX. The data showed that 91.6% of patients had overall efficacy as "marked improvement" or "improvement". Serious adverse reaction was reported in 6.2%. Therefore, IFX is very effective and well tolerated in Japanese patients with RA.