Inclusion Criteria: - Subjects with active rheumatoid arthritis as defined by ACR criteria - Able to start Enbrel® or Kineret® therapy (per the approved product monographs) within approximately 30 days of confirmed enrolment Exclusion Criteria: - Active infections at the time of initiating Enbrel® or Kineret® therapy - Malignancy other than basal cell carcinoma of the skin or, in situ carcinoma of the cervix, within the past 5 years - Known hypersensitivity to E. coli derived products - Known hypersensitivity to Enbrel® or any of its components - Subjects receiving, or who received:* Enbrel® in the previous 30 days; * Remicade® in the previous 3 months; * Humira® in the previous 3 months; * Kineret® in the previous 15 days. - Subjects beginning Enbrel® therapy, or treated with prior or current treatment using Enbrel® - Subjects beginning Kineret® therapy, or treated with prior or current treatment using Kineret® - Treatment with any investigational therapy in the 30 days prior to enrolment confirmation - Presence of any significant and uncontrolled medical condition which, in the investigator's opinion, precludes the use of Enbrel® - Sepsis or at risk of septic syndrome