OBJECTIVES: To estimate the cost-efficacy of infliximab and etanercept compared to placebo in psoriasis patients using 24-week Psoriasis Area and Severity Index (PASI) scores and average sales price (ASP). METHODS: For infliximab, dosed at 5mg/kg, the average number of vials per dose was 4.5 (patient weight of 90kg). The cost per patient per infusion was $2,658. The total infusions per patient per year was 8.75, and administration cost per infusion was $237.92. Etanercept assumed to be administered at 50 mg/dose twice a week for the first three months and at 25 mg/dose twice a week for the rest of the year. The cost of adverse events was not included in the cost-efficacy estimation. The PASI scores at 24 weeks were used as efficacy measures. Patients were included for PASI response if their baseline body surface area (BSA) psoriasis was >=10%. RESULTS: In the infliximab trial (EXPRESS), the number needed to treat (NNT) was 1.19, 1.28, and 1.75 for PASI 50, PASI 75, and PASI 90, respectively. In the etanercept trial (Papp trial), the NNT was 1.96 for PASI 75, (efficacy data unavailable for PASI 50 or PASI 90). For infliximab, based on the ASP + 6% (Q1' 07), the annual cost to achieve NNT for a PASI 75 was $29,401. The corresponding annual cost to achieve NNT based on the ASP + 6%, was $40,757 for a PASI 75 with etanercept. Thus, it cost $11,356 more to achieve a PASI 75 with etanercept, compared with using infliximab. CONCLUSION: The cost-efficacy measure based on the NNT and annual cost to achieve NNT showed meaningful differences between infliximab and etanercept. However, the cost-effectiveness in clinical practice will depend on the actual dose used, and the actual effectiveness achieved. Moreover, the incremental cost-effectiveness of one product compared to another cannot be reliably estimated without a head-to-head trial.