To study the relationship between mutation of the inverted repeat sequence (IR) in the multiple transferable resistant system (mtr) of Neisseria gonorrhoeae (NG) and itsmultiple antibiotic resistance, minimal inhibitory concentrations (MICs) for the clinically isolated strains were tested by agar-dilution-method. The mtr system's IR gene of NG was sequenced after amplification by polymerase chain reaction (PCR). Either two susce ptive or five penicillin-resistant strains had no base mutation in IR gene, while all of the 13 strains with multiple-antibiotic-resistance had a singlebase deletion (A/T). The result suggests that a single-base deletion of the thirteen-base IR sequence in mtr system of NG might result in multiple antibiotic resistance but is not associated with single antibiotic resistance.