The purpose of this study is to assess the effects (good and bad) of golimumab (CNTO 148) therapy in participants with ulcerative colitis (UC).

This is a multi-center (conducted in more than one center), randomized (study medication assigned by chance), double-blind (neither the physician nor the participant know about the study medication), placebo-controlled (an inactive substance that is compared with a drug to test whether the drug has a real effect in a clinical trial), parallel-group (a medical research study comparing the response in 2 or more groups of participants receiving different interventions) study to evaluate the safety and efficacy of golimumab in participants with moderately to severely active UC. There are 2 parts in this study. Part 1 is "Phase 2 dose-ranging" portion of study. Participants enrolled in Part 1, will receive subcutaneous (under the skin by way of a needle) injections of placebo, golimumab 100 milligram (mg), 200 mg, or 400 mg at Week 0, followed by subcutaneous injections of placebo, golimumab 50 mg, 100 mg, or 200 mg respectively at Week 2. Part 2 is "Phase 3 dose-confirming" portion of study and newly enrolled participants will receive same doses studied in Part 1, until the doses for Part 2 are selected. At the time that the final doses are selected, all newly enrolled participants will receive 1 of the selected doses or matching placebo. At Week 6, participants will be asked to participate in an additional 1-year maintenance study. Participants not entering the 1-year golimumab maintenance study will be evaluated for safety 16 weeks after last administration of study agent. The duration of study will be 6 weeks for participants who enter the 1-year golimumab maintenance study and 16 weeks after last administration of study agent for participants who do not enter the 1-year golimumab maintenance study. Efficacy of the participants will primarily be evaluated by clinical response at Week 6. Participants' safety will be monitored throughout the study.

Inclusion Criteria:

• Participants diagnosed with moderately to severely active ulcerative colitis (UC) defined by a Mayo score of 6 to 12 inclusive at Baseline (Week 0), including an endoscopic (examination of an internal part of the body with a lighted tube; looking at a part of the body with a lighted tube) subscore of greater than or equal to 2
• Participants must have biopsy results (collected at the screening endoscopy (procedure or obtained within the last year) consistent with the diagnosis of UC
• Participants either currently receiving treatment with, or have a history of failure to respond to, or tolerate, at least 1 of the following therapies: oral 5-aminosalicylate, oral corticosteroids, 6-mercaptopurine and azathioprine
• Participants with current dependency or with a history of corticosteroid dependency (i.e., an inability to successfully taper corticosteroids without a return of the symptoms of UC)
• Not have a diagnosis of active tuberculosis
• Participants with negative stool test for enteric (by way of the intestines) pathogens

Exclusion Criteria:

• Participants with prior exposure to biologic anti-tumor necrosis factor (TNF) agents
• Participants with severe extensive UC that is likely to require a colectomy (surgery to remove part or all of the colon) within 12 weeks of study entry
• Participants having UC limited to the rectum only or to less than 20 centimeter of the colon
• Presence of a stoma (an artificial permanent opening especially in the abdominal wall made in surgical procedures) or presence of a fistula
• Participants with a history of extensive colonic resection