Objective To assess the efficacy and safety of efalizumab in the treatment of psoriasis. Methods Randomized controlled trials (RCT) on efalizumab in the treatment of psoriasis were identified from The Cochrane Library ( issue 1, 2006) , specialized trials registered in Cochrane Skin Group (2006), MEDLINE (1966 - 2006) and EMBASE (1974 - 2006). The quality of the trials was assessed by two reviewers independently. RevMan 4.2.7 software provided by the Cochrane Collaboration was used for statistical analysis. Results Three RCTs involving 1 651 patients were included, all of which were of high methodological quality. All the patients were diagnosed as chronic moderate to severe plaque psoriasis with the age of 18-75 years. Meta-analysis indicated that at week 12, significantly more patients in both 1mg/kg/w and 2 mg/kg/w efalizumab subcutaneous groups achieved PASI50, PASI75, PASI90 improvement compared to the placebo group (Plt;0.0001), while there was no significant difference in PASI50, PASI75 and PASI90 responses between 1mg and 2mg efalizumab groups (P gt;0.05). No serious adverse effects were identified. Extended treatment for another 12w may contribute to further efficacy without increasing toxicty. Conclusions Efalizumab 12w therapy is safe and effective for treating adult patients with moderate to severe plaque psoriasis. More RCTs are required to assess the efficacy of the extended treatment.