The purpose of this study is to evaluate the safety and effectiveness of infliximab (an anti-TNF chimeric monoclonal antibody [cA2]) in patients with active Rheumatoid Arthritis, despite methotrexate treatment.

This is a placebo-controlled, double-blinded, randomized clinical study to evaluate the safety and effectiveness of infliximab in patients with active Rheumatoid Arthritis, despite methotrexate treatment. Infliximab is an anti-TNF chimeric monoclonal antibody (cA2). The primary measures of effectiveness include the change from baseline in American College of Rheumatology (ACR20) response at week 30, and the change in the modified van der Heijde Sharp Score. The ACR20 Responder Index a composite of clinical, laboratory, and functional measures and the van der Heijde-Sharp (vdH-S) scoring method is a method of rating structural damage in patients..

Patients will be treated with either infliximab or matching placebo.

Inclusion Criteria:

• Patients with active Rheumatoid Arthritis despite treatment with methotrexate
• Diagnosed with Rheumatoid Arthritis at least 6 months prior to screening
• Having active disease at the time of screening and pre-infusion as defined by having at least 6 or more swollen joints and 6 or more tender joints
• Using methotrexate for at least 3 months prior to study enrollment

Exclusion Criteria:

• Patients having any systemic inflammatory condition
• Having Lyme disease or a rheumatic disease other than Rheumatoid Arthritis
• Who have used Disease-Modifying Antirheumatic Drugs (DMARDs) other than methotrexate within 4 weeks prior to screening
• Who have used corticosteroids within 4 weeks prior to screening
• Having received previous administration of infliximab