To the Editor.— Recently, O'Toole et al called attention to an outbreak of methicillin-resistantStaphylococcus aureus(213:257,1970). We have reviewed the problem of methicillin resistance at Memorial Hospital for Cancer and Allied Diseases, New York, during a six-year period ( Feb 24, 1964 to Nov 25, 1969).. We were concerned whether methicillin resistance was occurring and could be reliably established by routine disk methods in a diagnostic microbiology laboratory. Antibiotic sensitivity was determined in the microbiology laboratory of the hospital by the disk sensitivity method; 5μg methicillin, 1μg oxacillin, and 30μg cephalothin disks were used. Of 6,209 cultures containing coagulase-positiveS aureus, 168 (2.7%) were resistant to methicillin during the study period. Of the 168 only 66 (1.1%) were resistant to both methicillin and oxacillin. Our hospital laboratory began testing the sensitivity ofS aureusto cephalothin on April 13, 1966. From that time until the conclusion of the study,