Aeromonas is widely distributed in environment. These bacterial will cause septicemia disease in aquatic animals. Some Aeromonas species also cause gastroenteritis diseases in humans. Because of its heterogenic virulence factors the pathogenicity of Aeromonas is wide. Further antibiotics are commonly using for control of bacterial diseases, but misuse of antibiotics leads to development of resistance. Hence this book will give the information about its distribution, epidemiology and virulence factors of it.