Twenty-four clinical isolates of Staphylococcus aureus collected from various geographic areas and four reference strains were studied by (i) agar diffusion with disks impregnated with 5 microg oxacillin and reading after incubation at 30C for 24 hours, (ii) Southern hybridization with a probe specific for the mecA gene, and (iii) the BBLreg CrystalTM MRSA ID system. There was perfect correlation between the three methods: the BBLreg CrystalTM MRSA ID system detected methicillin resistance in the fifteen strains hybridizing with the mecA probe and classified as resistant by the oxacillin disk diffusion test; the thirteen remaining strains were susceptible by agar diffusion and by the BBLreg test and did not hybridize with the mecA probe. The BBLreg CrystalTM MRSA ID System, therefore, appears to be an accurate method for rapid detection of Staphylococcus aureus exhibiting homogeneous resistance to methicillin.