A total of 129 clinical isolates of Staphylococcus species was characterized by the tests of coagulase production, haemagglutination, mannitol fermentation, DNase production and hemolysis. Ninety-nine out of them showed positive reactions to the tests, therefore they were identified as Staphylococcus aureus. The isolates showing positive reaction in haemagglutination test also showed 100% of tube coagulase positive reaction. The haemagglutination test was a reliable method for identifying Staphylococcus aureus in the clinical laboratory. S. aureus produced stronger hemolysis with human blood agar than with sheep blood agar. Antibiotic resistant S. aureus isolates(S-46, S-112, S-126) had 4 to 6 p]asmid DNA elements. The S-112 strain had 6 plasmid DNA elements(1.8, 2.2, 3.7, $26.3{sim}50$, and 70 Mdaltons), the S-126 had 4 elements(2.6, 4.2, $4.6{sim}60Md$), and the S-46 had 1 element(${sim}100Md$). PPSA strain had 4 plasmid DNA elements(2.5, 4.2, $4.6{sim}60Md$) and S. aureurs(ATCC) strain contained 9.4, 26.3 and ${sim}50Md$ plasmid DNA elements.