OBJECTIVE: To assess the efficacy and safety of golimumab in patients with active psoriatic arthritis (PsA). METHODS: Adult patients with PsA who had at least 3 swollen and 3 tender joints and active psoriasis were randomly assigned to receive subcutaneous injections of placebo (n = 113), golimumab 50 mg (n = 146), or golimumab 100 mg (n = 146) every 4 weeks through week 20. Efficacy assessments through week 24 included the American College of Rheumatology 20% improvement criteria (ACR20), the Psoriasis Area and Severity Index (PASI) in patients in whom at least 3% of the body surface area was affected by psoriasis at baseline, the Short Form 36 Health Survey (SF-36), the disability index of the Health Assessment Questionnaire (HAQ), the Nail Psoriasis Severity Index (NAPSI), the physician's global assessment of psoriatic nail disease, and enthesitis (using the PsA-modified Maastricht Ankylosing Spondylitis Enthesitis Score [MASES] index). RESULTS: At week 14, 48% of all patients receiving golimumab, 51% of patients receiving golimumab 50 mg, and 45% of patients receiving golimumab 100 mg achieved an ACR20 response (the primary end point), compared with 9% of patients receiving placebo (P < 0.001 for all comparisons). Among the 74% of patients in whom at least 3% of the body surface area was affected by psoriasis at baseline, 40% of those in the golimumab 50 mg group and 58% of those in the golimumab 100 mg group had at least 75% improvement in the PASI at week 14 (major secondary end point), compared with 3% of placebo-treated patients (P < 0.001 for both doses). Significant improvement was observed for other major secondary end points (the HAQ and the SF-36), the NAPSI, the physician's global assessment of psoriatric nail disease, and the PsA-modified MASES index in each golimumab group compared with placebo. This efficacy was maintained through week 24. Golimumab was generally well tolerated. CONCLUSION: Treatment with golimumab at doses of 50 mg and 100 mg significantly improved active PsA and associated skin and nail psoriasis through week 24.