The human population most commonly inflicted with Aeromonas infection includes young children, the elderly and immunocompromised individuals. Importantly, the isolation rate of Aeromonas species from children suffering from diarrhea is similar in developing and developed countries. It is becoming clear that only a small subset of Aeromonas species belonging to a particular hybridization group causes disease in humans. Human infections with this pathogen occur by consuming contaminated food and water. Aeromonas species were isolated from wounds of patients during the tsunami in southern Thailand. Further, increased numbers of this pathogen were recovered from floodwater samples during Hurricane Katrina in New Orleans. Among various species of Aeromonas, A. hydrophila, A. caviae and A. veronii biovar sobria are mainly responsible for causing disease in humans. Our laboratory has isolated various virulence factors from a diarrheal isolate SSU of A. hydrophila and molecularly characterized them. In addition to various virulence factors produced by Aeromonas species, the status of the immune system plays an important role in inducing disease by this pathogen in the host. Taken together, we have made significant advances in better understanding the pathogenesis of Aeromonas infections, which will help in differentiating pathogenic from non-pathogenic aeromonads. This review covers virulence aspects of a clinical isolate of A. hydrophila.