Sensitivities of 120 strains of Staphylococcus aureus to methicillin, cetylpyridinium chloride (CPC) and chlorhexidine (CH) were measured by the agar dilution technique. The MICs for CPC and CH were < or = 2 micrograms/ml in 93 and 83% of methicillin-sensitive S. aureus, respectively, and > 2 micrograms/ml in 81 and 83% of methicillin-resistant S. aureus (MRSA), respectively. Overall, the MICs for CPC and CH were 5-10 times greater in the methicillin-resistant than in the methicillin-sensitive strains (p < 0.001). The MICs for CPC and CH also predicted the relative susceptibilities of S. aureus strains to the bactericidal action of these agents in growth and time-kill studies. The possibility that antiseptics and disinfectants contribute to the selection and maintenance of multiply resistant MRSA is considered.