Background: The comparative efficacy and tolerability of conventional and biologic treatments for moderate-to-severe plaque psoriasis are unknown. Objectives: To perform a systematic review and meta-analysis of randomized controlled trials (RCTs) reporting efficacy of systemic treatments approved for moderate-to-severe psoriasis by means of the Psoriasis Area and Severity Index (PASI). Methods: We identified relevant articles by systematic electronic searches (Cochrane Library, Medline, Embase, Scopus). Efficacy was defined as proportion of participants with ≥ 75% decrease in PASI (PASI-75) at primary efficacy measurement (week 8-16). PASI-75 response rates of double-blind placebo-controlled trials were summarized as risk differences (RDs) and pooled using random effects models. Tolerability was assessed from rates of withdrawals and adverse events. Results: Twenty-four RCTs totalling 9384 patients were analysed qualitatively. Sixteen double-blind placebo-controlled trials were eligible for meta-analysis. Infliximab was significantly superior to all other interventions [RD 77%, 95% confidence interval (CI) 72-81%]. Adalimumab (RD 64%, 95% CI 61-68%) was superior to ciclosporin (RD 33%, 95% CI 13-52%), efalizumab (RD 24%, 95% CI 19-30%), etanercept 50 mg twice weekly (RD 44%, 95% CI 40-48%) and etanercept 25 mg twice weekly (RD 30%, 95% CI 25-35%). Efalizumab was significantly less efficacious than fumaric acid esters (RD 48%, 95% CI 32-64%). Rates of withdrawals due to adverse events were highest for methotrexate and fumaric acid esters. Conclusions: The efficacy of systemic agents approved for moderate-to-severe psoriasis differs considerably both within and between biologics and nonbiologics. Infliximab is most efficacious, followed by adalimumab. Patients receiving infliximab have an excess chance of 77% over placebo to achieve PASI-75 response. Published evidence questions regulatory guidelines that recommend biologics as second-line therapy for moderate-to-severe plaque psoriasis.