Knowledge of physiologic/phenotypic and genetic variation of Escherichia coli O157 and its tight clonality was the basis for development of successful detection protocols for Shiga toxin-producing E. coli (STEC) O157:H7/H. Phenotypic and genetic characteristics of diarrheagenic E. coli O26 isolates from different geographical regions may differ as indicated by representative reports from all continents. In this review, we summarize current knowledge on STEC O26, a pathogen whose emergence predates that of other STEC, including O157:H7/H-. The overall objectives are to integrate information available from peer-reviewed literature on the clinical and public health significance of STEC O26 worldwide, and to highlight phenotypic and genetic markers that could be used for routine detection of this pathogen. Our ultimate goal is to render information that will allow quick, accurate, and specific detection of STEC O26 genotypic variants worldwide, so as to aid with control of this pathogen. The information herein will be invaluable to a variety of scientists that include epidemiologists and microbiologists (medical, veterinary, food, and environmental) with interest in STEC O26--a zoonotic and emerging foodborne pathogen.