The pharmacokinetics and toxicity of six week courses of vancomycin were assessed prospectively in 12 chronic hemodialysis patients who had 17 episodes of Staphylococcus aureus bacteremia. Patients were treated with 1 gram doses of vancomycin at weekly intervals for six weeks. Peak serum vancomycin concentrations ranged from 5.5-40.0 micrograms/ml and trough concentrations were 1.0-12.0 micrograms/ml at the time of the second dose. No patients demonstrated important drug accumulation at the time of the fifth dose. Pure tone audiometry demonstrated no auditory toxicity. Flushing and pruritus (two patients) were only adverse effects noted. In 16 episodes blood cultures were sterilized within 48 hours of therapy. This investigation demonstrates that in chronic hemodialysis patients with S. aureus bacteremia vancomycin is a safe and microbiologically effective antimicrobial agent. Peak and trough serum concentrations vary widely when 1 gram doses are given at one week intervals, and thus it is recommended that concentrations be measured for each patient, particularly if the minimum bactericidal concentration of vancomycin for the clinical isolate is greater than 1.0 microgram/ml.