As revealed in the realization of the epidemiological surveillance of hospital infections caused by methicillin-resistant S. aureus (MRSA) in different types of hospital, MRSA strains causing purulent inflammatory diseases belong to different clones. The complex marking of MRSA made it possible to determine the presence of the same clone in different hospitals and to detect the outbreaks of hospital infections caused by different clones of MRSA in one hospital. It was found necessary to supplement the commercial international phage-typing set with pages permitting the detection of the specific system of restriction-modification in MRSA.