Between February 1992 and February 1993, 12 patients were seen who were infected or colonized with methicillin-resistant strains of Staphylococcus aureus. The strains had decreased susceptibility to teicoplanin (MICs, 8-16 micrograms/mL). Field inversion gel electrophoresis showed the strains belonged to three related clones (A1, A2, and A3). The patients were though to have acquired the strains nosocomially. Consistent with results of laboratory studies of teicoplanin-resistant S. aureus, all but 1 strain expressed a 35-kDa membrane protein, and 9 strains expressed increased levels of penicillin-binding protein 2 complex. Six strains were isolated from patients treated with glycopeptides. These data suggest that nosocomial transmission of S. aureus with decreased teicoplanin susceptibility may occur during glycopeptide use and that such strains develop resistance by a mechanism associated with the appearance of a 35-kDa membrane protein. Surveillance is necessary to monitor for the potential selection of resistant clones that may be capable of dissemination.