Background : Staphylococus aureus distribution is associated with the nasal and hand carriage in hospital staff and medical students. A factor associated with the virulence of disease is the ability of bacteria to produce the enterotoxins (Se) and Toxic shock syndrome toxin 1 (TSST -1). A problem in treatment was an increase in drug resistance particularly, resistance to methicillin grourp (MRSA). Objectives : To investigate and to compare the prevalence of nasal and hand carriage of Staphylococcus aureus in the hospital staffs and the medical students studying in the preclinical class (the third year) and in the clinical class (the fifth year) The occurrence of enterotoxin and TSST-1 production of Staphylococcus aureus isolated were examined. Moreover, drug resistance was also evaluated. Design : Survey and laboratory study. Setting : At Srinagarind hospital, Faculty of medicine, KKU Subjects : One hundred and eight hospital staff (phyusicians, nurses, workers) and 63 medical students (during their studies in preclinic and in clinic classes) were examined. Methods : Staphylococcus aureus were identiflied by coagulase test and sugar fermentation. The enterotoxin and TSST-1 production were detected by reersed passive latex agglutination. Drug resistance was tested by disk agar diffusion method. Results: No significant difference in the prevalence of nasal and hand carriage of Staphylococcus aureus was found between the hospital staff and the medical students in both years (55.6%-59.3% in anterior nares and 38.1%-44.4% in hands). MRSA was found in anterior nares and hands of the medical staff with 10.2% and 9.3% respectively. Those of the third year and the fifth year were found with 1.6%, 0% and 3.2%, 1.6% respectively. The enterotoxin and TSST-1 production occurred in 13.9% of anterior nares and 5.6% of hands of the hospital staff and were found more frequently in MSSA than in MRSA. The SeA was the most predominant enterotoxin isolated from both organs of the medical staff and was found in only the fifth year medical students. With the increasing clinical exposure (the fifth year), the more enterotoxins were found. The production of enterotoxins were found in 14.3% of anterior nares and 4.7% of hands of the fifth year medical students or 20.5% and 11.5% of total Staphylococcus aureus isolation whereas they were found in 7.9% of anterior nares and 4.7% of hands of the third year medical students or 11.9% and 9.7 of total Staphylococcus aureus isolation. TSST-1 was also found in strains isolated from both organs of the hospital staff but was not found in the medical students. Resistance to penicillin, tetracycline, lincomycin occurred more frequent respectively in strains isolated from both the hospital staff and the medical students. Conclusions : No significant difference of carriage of Staphylococcus aureus was found in the hospital staff and the medical students. Drug resistance was increased with increasing clinical exposure. The enterotoxin and TSST-1 productions and the type of enterotoxin combination were found more frequently in clinical exposed people than non clinical exposed people although there was no significant difference.