Verotoxin-producing Escherichia coli O157 is a primary cause of severe and bloody diarrhea. Campylobacter spp. are one of the commonly reported bacterial cause of gastrointestinal infections throughout the world. Only a few cases involving both E. coli O157 and Campylobacter species have been reported. The authors simultaneously isolated verotoxin-producing E. coli O157 and Campylobacter species from the stool of a 3 year-old male with bloody diarrhea, fever and abdominal pain. (Korean J Clin Microbiol 2004;7(2):186-189)