Isolated acute monoarticular septic arthritis of the sternoclavicular joint is a extremely rare disorder, and is usually associated with predisposing factors such as contiguous foci of infection, heroin addiction, rheumatoid arthritis, diabetes mellitus and maintenance hemodialysis. This case occurred in healthy adult. The etiological agent was staphylococcus aureus. Good result wads achieved by applying appropriate antibiotic therapy combined with an adequate drainage.