326 employees of 4 medical institutions (1 regional hospital, 2 city hospitals and a maternity clinic) were examined for the presence of S. aureus carriership. Examinations were made every 3 months for 3 recent years. The results of these examinations were compared with the distribution of the blood groups in the AB0 system among the carriers. Constant and malignant carrier state was detected mainly in persons with blood group A.