Of 50 patients with bacteremia due to Staphylococcus aureus but without clinical evidence of endocarditis, 24 developed antibodies to the cell wall teichoic acid of S. aureus that were demonstrable by counterimmunoelectrophoresis. However, only 16 of the 24 patients developed titers of antibodies high enough for detection by passive gel diffusion. Eleven of the 16 patients developed evidence of complications due to metastatic infection. In contrast, of the 34 patients who were antibody-negative by gel diffusion, only one patient developed evidence of metastatic seeding. Thus, the development of antibodies to teichoic acid at a level detectable by the gel diffusion technique is regularly associated with complicated infections due to S. aureus that require more prolonged therapy, whereas bacteremic patients not developing such an antibody response rarely develop complications and may be treated with a two-week course of therapy.