A retrospective study of 38 patients with established psoriasis treated by 55 Charnley low-friction arthroplasties showed a superficial infection rate of 9.1% and a deep infection rate of 5.5%. All of the operations were carried out in the Charnley clean-air enclosure, without prophylactic antibiotic therapy. The incidence of postoperative sepsis in psoriatic patients was significantly higher than in patients with osteoarthritis (p less than 0.001) and rheumatoid arthritis (p less than 0.05). Hence, prophylactic antibiotic therapy appears beneficial in psoriatic patients.