The Safe Drinking Water Act requires the U.S. Environmental Protection Agency (EPA) to publish regulations to control disease-causing organisms (pathogens) and hazardous chemicals in drinking water. Aeromonas hydrophila (A. hydrophila), a member of the genus Aeromonas, is listed on the first and second Contaminant Candidate List (CCL 1 and CCL 2) of potential waterborne pathogens (USEPA 1998; 2005). This document constitutes a comprehensive review of published literature on the genus Aeromonas, with emphasis on the biology of the organisms, their occurrence in the environment, their effects on human health, the methods by which they may be detected, and their response to water treatment technologies.