Risk factors for hip and knee prosthesis infection have been described, but not psoriasis. Eighty five infected patients from different centers and 202 non infected patients were included in a case-control study. Fifteen of 85 infected patients (17.6%), and 2 of 202 (1%) non infected patients had psoriasis. Odds ratio for infection in patients with psoriasis is 21.4 (4.7-195.5), and 39.7 (5.3-1718.8) in patients with hip prosthesis and psoriasis. No significant difference was found in patients with knee prosthesis. These data indicate that psoriasis is a risk factor for hip prostheses infection.