During the past 20 years, outbreaks of enterohemorrhagic Escherichia coli (EHEC) have been increasing worldwide and have been recognized as a potential health concern. Vero toxins produced by EHEC seem to be the most common cause of hemolytic uremic syndrome. Rapid diagnosis of EHEC infection is important to prevent the expansion of infection. Diagnosis is carried out by both isolation of EHEC and detection of Vero toxins in fecal extracts or fecal cultures. This review describes briefly about the current knowledge of the EHEC and Vero toxins, and about the determination methods for Vero toxins. The attempt to identify Vero toxins by electrospray ionization-liquid chromatography/mass spectrometry is also discussed.