Staphylococcus aureus strain DU4916 was examined for linkage of markers. No 'curing' action due to treatment with acridine dyes was demonstrated. The genes for penicillinase production and metal-ion resistance (borne by a plasmid of 20 x 106 daltons), tetracycline resistance (a plasmid of 2.9 x 106), streptomycin resistance (a chromosomal gene) and methicillin resistance (of uncertain locus) were separately transduced to recipients. No linkage of methicillin resistance with enterotoxin B, haemolysins, pigment, or a gene that suppresses inducible resistance to erythromycin was demonstrated. These data are consistent with the hypothesis that all methicillin-resistant strains of S. aureus have a common and relatively recent origin.