**Abstract**

Hemolysin is one of the major pathogenic factors among *Vibrio* species, which shows hemolytic activity against erythrocytes. It is associated with different *Vibrio* spp. that manifest either wound infection or intestinal infection as their clinical symptom. *V. vulnificus* and *V. alginolyticus* are well-known causative organisms for wound infection, whereas the gastrointestinal infection is caused by *V. cholerae*, *V. mimicus*, and *V. parahaemolyticus*. There are two major groups of hemolysins in *Vibrio* spp.: the thermostable direct hemolysin (TDH) from *V. parahaemolyticus* and the HlyA (El Tor hemolysin) from *V. cholerae*. These hemolysins have homology in certain degrees; however, the essential amino acids for the activity are variable depending on the species. This chapter summarizes the functions and features of hemolysins from *Vibrio* species, which has been reported so far.

**Keywords:** thermostable direct hemolysin, El Tor hemolysin, *Vibrio parahaemolyticus*, *vibrio cholerae*, *vibrio mimicus*, *vibrio vulnificus*
