Polymerase chain reaction (PCR) was applied for the detection of methicillin-resistant Staphylococcus aureus (MRSA). This procedure amplified a segment of MRSA-PBP (penicillin-binding protein) gene of DNA extract from the clinical isolates of S. aureus. A 1339-base-pair fragment of MRSA-PBP gene in DNA from S. aureus (MIC of methicillin, greater than or equal to 16 micrograms/ml) was amplified and detected by a specific oligonucleotide probe. Moreover, a 4.3 kb HindIII fragment containing MRSA-PBP gene was detected by using the same oligonucleotide probe. On the other hand, no PCR-amplified product was detected in DNA from methicillin-sensitive S. aureus (MIC of methicillin, less than 16 micrograms/ml).