Of eight patients with Gram-negative bacillary sternoarticular pyoarthrosis, seven were long-term intravenous heroin abusers. Clinical onset was insidious and a long delay (one month or more) in seeking hospitalization was usually noted. Anterior chest discomfort and painful, restricted homolateral shoulder motion were the chief complaints. Fever and monoarticular arthritis were universally present, Open synovial biopsy examination was frequently required for etiologic diagnosis. Pseudomonas aeruginosa was the most common pathogen isolated. Roentgenographic evidence of associated osteomyelitis was usually seen, but tomography was often necessary to delineate this lesion. Intraoperatively, associated osteomyelitis of the clavicular head and/or sternum was present in all eight cases and a perisynovial and/or retrosternal abscess was found in five patients. Early surgical exploration and prolonged antimicrobial therapy yielded excellent results.