Antibiotic multiresistant isolates of Staphylococcus aureus from outbreaks of nosocomial infection throughout Australia were found to possess essentially similar patterns of antibiotic resistance. Plasmid DNA profiles from these isolates exhibited a common pattern of large plasmids, of (15–22) × 10⁶ mol. wt, associated with resistance to gentamicin, kanamycin and tobramycin, plasmids of 3 × 10⁶ mol. wt, mediating resistance to chloramphenicol, and cryptic plasmids of 1 × 10⁶ mol. wt. Restriction endonuclease digestion confirmed the presence of related plasmids in isolates from all the hospitals that were surveyed. The homogeneity of these organisms suggests the dissemination of a multiresistant, plasmid-bearing strain of S. aureus, or its derivatives, among geographically-separated hospitals in Australia.