Septic arthritis is a serious and sometimes fatal complication of rheumatoid arthritis. We have examined the clinical characteristics of 16 patients with infectious arthritis seen during an eight-year period. This represented 0.5% of all admissions to our hospital for patients with rheumatoid arthritis. Although rheumatoid arthritis is considered a predisposing factor for joint sepsis, 15 of our patients had other conditions that most likely increased their susceptibility to infection. Many patients lacked distinctive features of joint sepsis (fever, chills) and only one half had leukocytosis. Six had polyarticular complaints despite documented monarthric sepsis. Delay in diagnosis of joint infection and persistent effusions of the infected joints portended a poor prognosis.