Background: Avascular necrosis (AVN) and psoriasis have some pathogenic mechanisms and associated conditions in common. Objective: To examine the association between psoriasis and AVN. Methods: This study used data from the Taiwan National Health Insurance Research Database for the period 2004-2006 and identified 28,268 patients with psoriasis, who were then matched for age and sex with 113,072 controls without psoriasis from the Taiwan Longitudinal Health Insurance Database 2000. Multivariate Cox proportional hazards models were used for the analysis. Results: The unadjusted risk of AVN was significantly higher for patients with psoriasis than for controls (hazard ratio [HR] 2.29) and remained significant after adjustment for other risk factors (adjusted HR 1.96; 95% confidence interval 1.62-2.38). The risk for AVN increased in relation to psoriasis severity and was higher for patients with psoriasis and arthritis than for patients without arthritis. The adjusted HRs were higher for male patients than for female patients and for patients younger than 30 years compared with older patients. Limitations: We lacked information on daily tobacco use, alcohol consumption, and physical activity. Conclusion: The risk for AVN increased with the disease severity of psoriasis.