The in vitro activity of the new glycopeptide antibiotic SK&F 104662 against problematic gram-positive microorganisms was determined using the agar dilution technique. For comparison, ampicillin, oxacillin, vancomycin, erythromycin and gentamicin were tested. SK&F 104662 was found to have high activity against Staphylococcus aureus, coagulase-negative staphylococci (both methicillin sensitive and resistant strains), Enterococcus faecalis, Enterococcus faecium, Listeria monocytogenes, Corynebacterium jeikeium and Corynebacterium group D2. All of 254 isolates, except one vancomycin-resistant strain of Enterococcus faecium, were inhibited by 2 mg/l of SK&F 104662; this compound may thus be potentially useful in the treatment of infections with the above-mentioned gram-positive pathogens.