Vibrio is a diverse genus of naturally occurring aquatic bacteria. A few of the Vibrio species are pathogenic to humans, most notably Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae. Illness from vibrios generally is due to consumption of raw or undercooked seafood. Vibriosis can range from mild gastroenteritis typical of a V. parahaemolyticus infection to severe septicemia and death with V. vulnificus infections. Details of Vibrio ecology, prevalence in seafood, disease frequency, and an overview of identification methods are included.