A prospective study of all cases of Staphylococcus aureus bacteremia (SAB) has been ongoing at our institution since April 1983. Data collected as of December 1984 reveal that of 79 episodes of SAB identified, 28 (35%) were caused by infected intravenous catheters; 14 of these were peripheral catheters and 14 were subclavian catheters. Endocarditis or metastatic infection was not recognized; two patients, one with a prosthetic heart valve and the other with recurrent SAB, did not meet the criteria for these complications but the clinical circumstances were strongly suggestive. Six of the 28 patients (21%) died of their infection, and local complications (inflammation or purulent drainage at the insertion site) were common. Only four of 22 patients who recovered were administered antibiotics for greater than 14 days. We conclude that patients with SAB caused by an infected intravenous catheter have a low risk of endocarditis or metastatic infection when the infected catheter is promptly removed and no risk factors (valvular heart disease or a prosthetic valve) are present that favor development of endocarditis. The duration of antimicrobial therapy need not exceed 2 weeks in this situation. The mortality related to SAB, however, was high and emphasizes the need to develop methods to prevent this infection.