BACKGROUNDEffective psoriasis therapies are needed for long-term symptom control.OBJECTIVEAssess efalizumab (Raptiva) efficacy in a large cohort of psoriasis patients.METHODSData from three Phase III, randomized, double-blind, parallel-group, placebo-controlled, multicenter studies were pooled. Patients (n = 1,651) with moderate to severe plaque psoriasis received 12 weeks of subcutaneous efalizumab 1 or 2 mg/kg/wk or placebo.RESULTSAll efficacy measures reached statistical significance within each of the individual studies (p < 0.001) and overall. More efalizumab-treated patients achieved > or = 75% and > or = 50% Psoriasis Area and Severity Index (PASI) improvement at week 12 than did placebo-treated patients (27.8% vs 3.8% [p < 0.001] and 56.1% vs 14.6% [p < 0.001], respectively). Significant PASI improvements occurred as early as week 2 (12.5% vs 7.9%, p =0.0001). Adverse events were generally mild to moderate.CONCLUSIONEfalizumab resulted in early and significant improvement for all efficacy endpoints and was well tolerated in patients with moderate to severe chronic plaque psoriasis.