OBJECTIVES: Studies have estimated the cost of biologics needed to achieve an additional responder as measured by Psoriasis Area and Severity Index (PASI) 75and PASI 90; however, limited information is available including PASI 100.  The purpose of this analysis was to evaluate the cost per additional responder associated with biologics for PASI 75, PASI 90 and PASI 100. METHODS: A literature review was conducted to identify randomized controlled trials and meta-analyses that included information on PASI 75, PASI 90 or PASI 100 and associated number needed to treat (NNT) compared to placebo for adalimumab (ADA), etanercept (ETN), infliximab (IFX), and ustekinumab (UST).  NNT was calculated as the inverse of absolute risk reduction from placebo.  The Wholesale Acquisition Costs for each biologic incurred during 12 weeks of treatment from initiation were determined using Analy$ource^® data as of November 2014.  Administration costs were not included.  Cost per additional responder was calculated as the NNT multiplied by 12 week drug costs. RESULTS: Cost per additional responder for PASI 75 was lowest for ADA ($18,065 - $18,647) and IFX ($18,101 - $19,493) followed by UST 45mg ($23,903 - $24,516), ETN ($37,825 - $41,036), and UST 90mg ($45,048 - $48,418).  Cost per additional responder for PASI 90 was lowest for ADA ($26,805 – $30,418) and IFX ($27,569 - $30,632) followed by UST 45mg ($38,765 - $39,532), UST 90mg ($71,095 - $88,256) and ETN ($84,749 - $89,209).  Limited data were available on PASI 100; however, cost per additional responder was found to be higher than PASI 75 and PASI 90 based on available data.  CONCLUSIONS: Cost per additional responder was higher for PASI 90 and PASI 100 given the greater NNT for each measure respectively.  Understanding the association between costs and NNT across various levels of efficacy may be valuable for decision makers when evaluating multiple medications.