This is a global registry, to evaluate the long-term safety of Humira® in patients with moderate to severe polyarticular Juvenile Idiopathic Arthritis (JIA), that are treated as recommended in the Humira® product label. Patients treated with MTX will be considered a reference group. Patients will be followed in both the Humira® and Methotrexate (MTX) arms for 10 years from the enrollment date into one of the treatment arms.

This registry will assess the incidence and rate of Humira (monotherapy or combination therapy with MTX) or MTX observational and treatment-emergent SAEs, Adverse Events of Special Interest (AESI) and Pregnancy in patients diagnosed with moderately to severely active polyarticular or polyarticular-course JIA through Year 5. From Year 6 through Year 10 SAEs, a subset of AESI that includes congestive heart failure (CHF), malignancies, AEs at least possibly related to and/or leading to discontinuation of registry treatment and pregnancies will be collected. For JIA patients 2 to< 4 years of age in countries with available local approval for this group of patients at the time of consent to the registry, emergent AESI, SAEs and pregnancy (at the age when a patient can become pregnant) will be collected for the full 10 years. The approved age range for HUMIRA in the U.S., European Union (EU) and in Australia is 4 years of age and older, and recent approval in EU for JIA patients 2 to < 4 years of age.

Patients who discontinue from the registry before 10 years will be offered to participate in the direct to Health Care Provider follow-up process, as allowed by local regulations.

Inclusion Criteria:

• For a patient enrolling into the HUMIRA® arm; a pediatric patient diagnosed at any time with moderately to severely active polyarticular or polyarticular-course JIA (defined as arthritis affecting >= 5 joints at the time of diagnosis of polyarticular or polyarticular-course JIA) who has been prescribed HUMIRA® therapy according to the local approved HUMIRA® product labeling and meets one of the following criteria:
• Enrolled patients are 4 to 17 years of age as per approved HUMIRA® product label with the addition of JIA patients 2 to < 4 years of age in countries with available local approval for this group of patients at the time of consent to the registry.
• Newly initiated (within 24 months of registry entry) on HUMIRA® therapy and has received continuous (no more than 70 consecutive days off drug) HUMIRA® therapy, and the physician can provide available source documentation of SAEs, AEs of Special Interest, and dosing information since initiation of therapy;
• Or is entering after participation (within 24 months of registry entry or, if longer, continuously treated at the same site) in an AbbVie Humira sponsored study, regardless of age or the number of joints with symptoms of JIA, and has received continuous (no more than 70 consecutive days off drug) HUMIRA® therapy and the physician can provide available source documentation of SAEs, AEs of Special Interest, and dosing information since initiation of therapy.
• For a patient enrolling into the MTX arm; a pediatric patient diagnosed at any time with moderately to severely active polyarticular or polyarticular-course JIA (defined as arthritis affecting >= 5 joints at the time of diagnosis of polyarticular or polyarticular-course JIA) who is prescribed MTX therapy alone or in combination with other disease modifying anti-rheumatic drugs (DMARDs) according to the local product labeling (initiated treatment within 24 months of registry entry) and has received continuous therapy and the physician can available provide source documentation of SAEs, AEs of Special Interest, and dosing information since initiation of therapy.
• Patients who were treated in the MTX arm of this registry and prematurely discontinued from the MTX arm due to being a non-responder, or became intolerant of MTX treatment or are in need of combination treatment with HUMIRA® therapy may be eligible to enroll into the HUMIRA® treatment arm if all ongoing AEs/SAEs have been resolved, and they meet inclusion criteria and can enroll within the registry enrollment period. In case of ongoing AEs/SAEs at the time of the treatment arm switch, the AbbVie Designated Physician should be contacted to assess the eligibility of patient to roll into Humira treatment arm.
• Parent or guardian has voluntarily signed and dated an informed consent/patient authorization form, approved by an Institutional Review Board (IRB)/Independent Ethics Committee (IEC) if applicable according to local law, after the nature of the registry has been explained and the patient's parent or legal guardian has had the opportunity to ask questions. Pediatric patients will be included in all discussions as per applicable local regulations in order to obtain verbal or written assent.

Exclusion Criteria:

• Patients should not be enrolled into the HUMIRA® or Methotrexate (MTX) arm if they cannot be prescribed and treated in accordance with the approved local HUMIRA® and/or with the local MTX product label
• Patients should not be enrolled into the HUMIRA® or MTX arm if they require on-going treatment with Kineret® (anakinra), Orencia® (abatacept), Rituxan® (rituximab), Enbrel® (etanercept), and Remicade® (infliximab), or any other approved biologic agents or investigational agents.
• Patients should not be enrolled into the MTX arm if they have had prior treatment with any investigational agent or anti-rheumatic biologic therapy such as, but not limited to, Orencia® (abatacept), Enbrel® (etanercept), Remicade® (infliximab), Rituxan® (rituximab), or Actemra® (tocilizumab)

Patients who are diagnosed at any time with moderately to severely active polyarticular or polyarticular-course JIA, (defined as arthritis affecting greater than 5 joints at the time of diagnosis of polyarticular or polyarticular-course JIA), prescribed and treated in a routine clinical setting either with Humira® (adalimumab), or MTX. Approximately 800 patients will be enrolled in the United States, EU countries, and Australia. Approximately 40 to 45 physicians will be included based on participation in prior AbbVie Humira sponsored clinical JIA studies.