1) The nasal-carrier rate of Staphylococcus aureus among 188 medical personnel(docters and nurses) who worked on 350 beds, Seoul National University Hospital during the period July I , 1960 to September 30, 1960 is studied and discussed. Thirtyeight per cent were found to be carriers. The highest carrier rate(66. 7%) were noted in the intern group, followed by resident (42.9%) and the lowest rate (25.0%) was found among staff physician category. During the same study period, nine (16. 9%) out of 53 normal new born babies were found to be harvoring Staphylococcus aureus in their short neonatal shpital stay. The carrier rate was in direct parallelism with the length of their hospital stay. 3) Fourty per cent of 50 patients admitted to the general surgical ward during the same period were found to have hemolytic , coagulase-positive Staphylococcus aureus in nose when cultured during the hospital stay.