ABSTRACTMultilocus sequence typing (MLST) has been proven useful for the study of the global population structure of Campylobacter jejuni; however, its usefulness for the investigation of outbreaks of disease caused by C. jejunihas not been proven. In this study, MLST plus sequencing of the flaAshort variable region (SVR) were applied to 47 isolates from 12 outbreaks of C. jejuniinfection whose relatedness has been determined previously, and the results were compared to those of serotyping and pulsed-field gel electrophoresis (PFGE). Isolates implicated in an outbreak were indistinguishable by all four subtyping methods, with sporadic isolates being distinguished from outbreak isolates. Two sporadic isolates from one outbreak were resistant to SmaI digestion and therefore nontypeable by PFGE but were differentiated from the outbreak strain by the other methods. PFGE and flaASVR typing were the most discriminatory methods, with discriminatory indices (DI) of 0.930 and 0.923, respectively. However, an epidemic strain from one outbreak was distinguished from the other outbreak isolates by flaASVR typing; its flaAallele was different at five nucleotides, suggesting that this change was possibly mediated by recombination. MLST was less discriminatory than PFGE and flaASVR typing (DI = 0.859), and many of the epidemic strains possessed common sequence types (STs) including ST-8, -21, -22, and -42. However, further discrimination within STs was achieved by flaASVR typing or PFGE. The results from this study demonstrate that a combined approach of MLST plus flaASVR typing provides a level of discrimination equivalent to PFGE for outbreak investigations.