Increasing epidemiological evidence suggests independent associations between psoriasis and cardiovascular and metabolic disease. Our objective was to test the hypothesis that directly assessed psoriasis severity relates to the prevalence of metabolic syndrome and its components. A population-based, cross-sectional study was undertaken using computerized medical records from the Health Improvement Network Study population including individuals in the age group of 45-65 years with psoriasis and practice-matched controls. The diagnosis and extent of psoriasis were determined using provider-based questionnaires. Metabolic syndrome was defined using the National Cholesterol Education Program Adult Treatment Panel III criteria. A total of 44,715 individuals were included: 4,065 with psoriasis and 40,650 controls. In all, 2,044 participants had mild psoriasis (2% body surface area (BSA)), 1,377 had moderate psoriasis (3-10% BSA), and 475 had severe psoriasis (>10% BSA). Psoriasis was associated with metabolic syndrome, adjusted odds ratio (adj. OR 1.41, 95% confidence interval (CI) 1.31-1.51), varying in a "dose-response" manner, from mild (adj. OR 1.22, 95% CI 1.11-1.35) to severe psoriasis (adj. OR 1.98, 95% CI 1.62-2.43). Psoriasis is associated with metabolic syndrome and the association increases with increasing disease severity. Furthermore, associations with obesity, hypertriglyceridemia, and hyperglycemia increase with increasing disease severity independently of other metabolic syndrome components. These findings suggest that screening for metabolic disease should be considered for psoriasis, especially when it is severe.