Because enterococci are typically tolerant of the bactericidal effects of cell wall-active antimicrobial agents, bactericidal therapy has required use of these agents in combination with aminoglycosides. For strains which do not demonstrate high-level aminoglycoside resistance, either streptomycin or gentamicin can be used in combination with penicillin, ampicillin or vancomycin. At some centers, as many as 50% of isolates display high-level gentamicin resistance. A minority of such isolates will not be highly streptomycin-resistant, and the latter drug can be used in combination with a cell wall-active drug. Optimal treatment of serious infections due to strains highly resistant to both streptomycin and gentamicin is unknown. While no agent is predictably bactericidal against such isolates, ampicillin, penicillin or vancomycin alone would be expected to cure some patients. Other drugs or drug combinations do not offer any predictable therapeutic advantages.