Two new glycylcyclines, CL 329, 998 and CL 331, 002, were tested for in-vitro activity against 178 clinical strains of enterococci which were resistant to one or more of the commonly used agents (ampicillin, high level gentamicin, vancomycin and teicoplanin). Both glycylcyclines demonstrated good activity (MICs ≤0·5mg/L) against all isolates tested, including those strains which demonstrated multiple resistance. As resistant enterococci are increasing in importance, new agents with activity against these strains are urgently required. Glycylcyclines have in-vitro activity which suggests they may be useful agents for treatment of infections caused by these organisms.