OBJECTIVE: There have been tremendous advances in treatment for patients with extensive psoriasis. Many of the newer treatments have shown great promise, but at a significant cost to the health care system. Office phototherapy treatments continue to be an excellent first choice because of high safety, good efficacy and relatively low cost. Unfortunately, office phototherapy may not be feasible for many patients. Home UVB offers another option for these patients. The purpose of this study is to assess the long-term financial cost of home UVB treatment. METHODS: We constructed a societal cost model for owning and operating a home UVB unit over a period of 30 years. This model included both direct and indirect costs associated with home treatment and periodic follow-up. These data were compared to the cost of other monotherapies for extensive psoriasis. RESULTS: The discounted present value of 30 years of treatment with home UVB was approximately $10,000. The initial one time cost of the home UVB device, approximately $2000, is only a small component of the lifetime cost. Over the same treatment period, methotrexate had an estimated cost of $23,530. The cost of one year of biologic treatment exceeded the lifetime cost of home UVB. CONCLUSIONS: Home UVB is not for every patient with psoriasis. Highly inflammatory lesions or significant co-existent arthritis are just two of many reasons that systemic treatments may be required. Nevertheless, home UVB offers a very cost-efficient approach to treatment. Insurers should make this option more available to patients with extensive psoriasis.