The in vitro antibacterial activity of teicoplanin, a new glycopeptide antibiotic, previously named teichomycin A2, has been compared to that of five other chemoantibiotics: netilmicin, clindamycin, rifampicin, enoxacin and vancomycin. The minimum inhibitory concentration (MIC) values against 588 gram-positive strains, 561 facultative aerobes and 27 anaerobes, recently isolated from clinical specimens, were evaluated. Teicoplanin showed the highest activity against all the tested strains, with a geometrical mean of the MICs (GMM), a MIC50 and MIC90 of 0.123, 0.12 and 0.5 micrograms/ml respectively.