The aim of this study was to examine the relationship between measures of disease severity and costs from a socie-tal perspective in patients with plaque psoriasis. Dermatologists in Sweden recruited 443 consecutive patients who had had no biological treatment during the past 12 months. Following a Psoriasis Area and Severity Index (PASI) assessment, subjects completed self-assessments on health status/quality of life and a healthcare resource utilization/work status questionnaire. The costs of healthcare resources and sick-leave due to plaque psoriasis were estimated and related to the subject's health status. A patient's Dermatology Life Quality Index (DLQI) and being on systemic therapy, or having diagnosis of psoriatic arthritis, appeared to be more strongly associated with direct and indirect costs than did their PASI. The cost of biological therapy should be considered from the perspective of the already high costs of patients with high DLQI undergoing traditional systemic treatment.