There is little published on the relative costs of treatments in psoriasis. OBJECTIVE: This study was designed to assess patterns of medication use, costs and health care resource utilization among US managed care psoriasis patients. METHODS: Members of 4 HMO's were identified using pharmacy outpatient and hospital claims data for a 1 year period. Patients were selected if they had 1) at least 2 claims for psoriasis (ICD-9 code 696, 696.1 and/or 696.8) or 2) 1 claim for psoriasis and 1 claim for a psoriasis drug or phototherapy. Descriptive data were collected to determine psoriasis drug and therapy use, and total and psoriasis specific costs. RESULTS: There were 2868 members with psoriasis identified. The data showed that 47.4% of the patients were on monotherapy and 45% of the patients were on polytherapy, defined as two or more of the psoriasis specific drugs or therapies. This coincides with recent market evaluations of psoriasis therapies. Topical corticosteroids were used by 82% of the patients. Claims for photochemotherapy were made by 9% of members. Eighty percent of patients received therapy from a dermatologist. There were psoriasis related hospitalizations for 11% of the patients. The median costs for psoriasis related hospitalizations/patient were $252-$1,383 (range:$40-18,933). Median total psoriasis related costs/patient were $155-$170 (range: $0-$24,333.77). CONCLUSION: High potency topical corticosteroids remain the most commonly used medications for psoriasis. Eventhough, few patients were hospitalized for psoriasis, the high costs of hospitalization made it one of the cost drivers of this condition. Phototherapy procedures, office visits for non-psoriasis specific diagnoses and total drug costs for psoriasis were additional cost drivers of psoriasis treatment.