The incidence of Haemophilus influenzae infections appears to be increasing although disease in adults due to this organism remains unusual. Only 16 cases of septic arthritis caused by this agent were found in a review of the literature. Two additional cases are reported and a summary of the clinical characteristics of these patients is presented. In general, females are affected more commonly than males, and blacks more often than whites. Joint involvement may be single or multiple, and associated or underlying conditions are frequent. Treatment with a variety of antimicrobials was generally successful and 87% of the infected joints was restored to pre-infection status. There were no specific characteristics in the clinical presentation which would allow an early precise etiologic diagnosis.