MONARTICULAR bacterial arthritis of the sternoclavicular joint appears to be rare. Arlet and Ficat1 reported one proved and one probable case of staphylococcal infection of this joint. Members of our group2 reported this joint involved once in 84 joints affected by bacterial arthritis. Waring3 states that bacterial arthritis of either the acromioclavicular or the sternoclavicular joint is rare except in polyarticular bacterial arthritis. We wish to report 2 additional cases recently encountered. Report of Cases Case 1.— A 59-year-old male had stiffness and soreness of his left shoulder that came on quickly in October, 1959, and he had 1° of fever. He was admitted to his local hospital with a diagnosis of pneumonia and received antibiotic therapy for 12 days. On dismissal from the hospital he was told that possibly he had a tumor in the apex of his left lung. He came to the