We developed and studied a molecular typing approach for Campylobacter spp. with restriction fragment length polymorphism (RFLP) analysis of the flagellin geneflaA in C. jejuni. Using polymerase chain reaction, we amplified theJfaA gene from strains comprising different HL:O serotypes by using a primer set directed at the conserved 5' and 3'flaA gene sequence to generate a 1.7-kb amplicon. The amplicon was further digested with the restriction enzyme DdeI, and the fragments generated were analyzed by agarose gel electrophoresis. In 43 non-outbreak strains of six common HL serotypes (HL 1, 2, 4, 5, 9, and 36) in the United States, 18 RFLP patterns were observed. In U.S. outbreak strains previously studied by 10 other typing methods, faA typing correlated with the HL serotype within each outbreak, and six additionalflaA types were identified. Our results suggest that RFLP analysis of theflaA gene from Campylobacter spp. has sufficient discrimination to be useful as a practical typing method for clinical and epidemiologic investigations.