Salmonella typhi, the etiologic agent of typhoid fever, typically has only a phase-1 flagellar antigen, HI-d (fliC). While most strains of S. typhi have HI-d antigen, 10–20% of Indonesian isolates have been reported to possess HI-j antigen instead. To investigate the presence HI-j strains of S. typhi isolates in Korea, where typhoid fever is still a common infectious problem, we used the polymerase chain reaction (PCR) with a pair of oligonucleotides primers that specifically amplified the flagellin gene of S. typhi. Of 375 isolates of S. typhi tested, only one was shown to possess the HI-j antigen, which was shown by the presence of a 1,269-basepair fragment on agarose gel electrophoresis after the PCR. The isolate with the HI-j antigen was cultured from a Korean-Indonesian man who was already symptomatic in Indonesia and was thought to be an Indonesian strain. Because 375 strains tested in this study were collected from cases with typhoid fever in different regions of Korea during the period from 1986 to 1991, it could be concluded that the mutation rate to j antigen is negligible among S. typhi endemic in Korea.