The economic burden of psoriasis varies by disease severity. Moderate to severe psoriasis requires use of systemic treatment agents and is likely to be associated with higher medical costs. OBJECTIVE: To estimate health care utilization rates and per-patient costs for the treatment of moderate to severe psoriasis. METHODS: A database of health insurance claims from 58 US commercial health plans was used to obtain patient-level data. Patients, aged 18-64, included in the analysis had a diagnosis of psoriasis, and received >1 treatment cycle of at least one of the following systemic agents: psoralen plus ultraviolet A (PUVA), methotrexate (Mtx), cyclosporine, acitretin, etretinate, ultraviolet B (UVB), and systemic corticosteroids (Cs). Patients with <6 months of observation period and those with rheumatoid arthritis and other autoimmune diseases were excluded from the analysis. RESULTS: A total of 1780 patients met all eligibility criteria noted above (Group 1). Another 282 patients were newly diagnosed patients with no prior history of claims for psoriasis (New Starts; Group 2). The most frequently used systemic therapies by patients in Group 1, over a period of 1 year, were Cs (42%), UVB (37%), PUVA (26%), and Mtx (22%). Of patients in Group 2, 56%, 37%, 31%, and 18% received UVB, Cs, PUVA, and Mtx. In an analysis of annual per-patient costs for drugs, outpatient services, and inpatient services, results were comparable for Groups 1 and 2. In Group 1, mean (median) annual per-patient costs were $917 ($473), $199 ($85), and $6 ($0), respectively and the corresponding costs for Group 2 were $744 ($412), $179 ($63), and $0 ($0), respectively. 90th percentile annual per-patient costs among all patients and New Starts were $2932 and $2125, respectively. CONCLUSIONS: Estimates of annual per-patient costs of treating moderate to severe psoriasis exceed those reported previously, and reflect a considerable direct medical burden.