Two-dimensional get electrophoresis (2-DE) was performed to examine exoproteins and periplasmic proteins of Shiga toxin-producing Escherichia coli (STEC) 0157:H7 strains isolated from cases associated with radish sprouts in two outbreaks. We found that STEC 0157:H7 released a large number of proteins into the medium during the stationary phase of growth, as observed with 2-DE. Although pulsed-field gel electrophoresis (PFGE) patterns of STECs NGY9 (RIMD0509894), a Sakai isolate; NGY33, a Gamagoori isolate; and NGY120, a Kanagawa isolate, were all the same, comparison of 2-DE patterns of exoproteins and periplasmic proteins clarified that NGY9 was distinct from NGY33, whereas NGY33 and NGY120 were of close lineage. We therefore suggest that 2-DE analysis of exoproteins and periplasmic proteins is a powerful epidemiological method with high resolution.