Drug resistance in Staphylococcus aureus is frequently mediated by non-chromosomal DNA molecules referred to as R plasmids. So far, resistance to aminosidic antibiotics was observed with streptomycin [8] and kanamycin-neomycin [3]. Resistance to gentamycin has not been reported in a recent survey by Lacey [7]. In this paper, we describe a strain of S. aureus resistant to gentamycin-kanamycin-tobramycin-sisomycin, and experiments which suggest that the genetic determinant of these resistance characters is plasmid borne.