The purpose of this study is to evaluate the pharmacokinetics (what the body does to the study medication) and safety of subcutaneously (under the skin) administered golimumab in pediatric participants (aged 2 to 17 years) with moderately to severely active Ulcerative Colitis (UC).

This is an open-label (both [participants and investigator] know what treatment participants will receive) and multicenter study. The study is divided into 2 parts: Part 1: pharmacokinetics portion (Week 0 to Week 14); Part 2: study extension (Week 14 to Week 114). The focus of this study is to evaluate the pharmacokinetics and safety of golimumab. Additionally the efficacy of short-term therapy with golimumab will be evaluated. Participants in clinical response at Week 6 will continue to receive open label golimumab maintenance therapy and will enter the study extension at Week 14. Participants who are not in clinical response at Week 6 will be withdrawn from further treatment with golimumab. At Week 114, participants who, in the opinion of the investigator, may benefit from continued treatment will be eligible to continue to receive golimumab every 4 weeks until marketing authorization is obtained in the treatment of pediatric UC in that country, or until a decision has been made not to pursue an indication in pediatric UC. Approximately 30 participants will be enrolled in this study. The total duration of study participation for a participant will be approximately 126 weeks or longer.

Inclusion criteria:

• Moderate to severe Ulcerative Colitis (UC) defined by a Mayo score (a score used to assess the treatment for UC) of 6 to 12 inclusive, including an endoscopic subscore of 2 or more.
• Must either be currently receiving treatment with, or have a history of having failed to respond to, or have a medical contraindication to at least 1 of the following therapies: oral or intravenous corticosteroids, 6-mercaptopurine and azathioprine OR must either have or have had a history of corticosteroid dependency (ie, an inability to successfully taper corticosteroids without a return of the symptoms of UC) OR required more than 3 courses of corticosteroids in the past year
• No history of latent or active tuberculosis prior to screening
• Positive protective antibody titers to varicella and measles prior to the first administration of study agent

Exclusion criteria:

• Have severe extensive UC that is likely to require a colectomy (surgical removal of the colon) within 12 weeks of study entry
• Have UC limited to the rectum only or to less than 20 cm of the colon
• Presence of a stoma
• Presence or history of a fistula
• Have evidence of Crohn's disease (an inflammatory large intestine disease)
• Previous exposure to anti-tumor necrosis factor therapy