The cases of 15 patients with 16 septic glenohumeral joints were evaluated. In each of the patients there was at least 1 predisposing factor, and each patient was treated by either repeated aspiration (11 shoulders) or arthrotomy (5 shoulders), combined with parenteral antibiotics. The most significant factors leading to poor results of treatment were delay in instituting treatment, virulence of the infecting organism, and a serious underlying disease process. In 8 of 10 shoulders in which treatment was begun 4 wk or less after symptoms appeared, a satisfactory functional outcome was obtained, while all 6 patients who were treated after a delay of more than 4 wk had poor results. All 6 patients infected with Streptococcus or coagulase-negative Staphylococcus had satisfactory results. Two of the 8 patients with Staphylococcus aureus or gram-negative organisms also had a satisfactory result, while the other 6 did not. The 2 successfully treated patients with Staphylococcus aureus were diagnosed within 3 days of the onset of symptoms, whereas the others had delays in instituting treatment.