We experienced two patients having Aeromonas species infection with severe clinical manifestations. The one patient was a 15-year-old high school girl student, who had been healthy in her school life, was admitted to the hospital with a sudden onset of left thigh muscle pain and swelling. She subsequently went into septic shock and died one day after admission. Pathological examination on autopsy revealed massive gas formation, skin bullas and ulcers, and extensive severe soft tissue damage throughout the body. Also, all the specimens, including brain, liver, spleen, thigh muscle, and blood in cardiac cavity, were positive for A. veronii biovar sobria. The other patient was 35-year-old man, who suffered from multiple bone fractures during the work in the harbor. One day after admission, he became febrile and went into septic shock. With the presumptive diagnosis of sepsis and gas gangrene, amputation of left thigh was performed. The exudate and aspirate of the amputated portion were repeatedly positive for A. hydrophila. Through the surveillance in Okinawa, Kagoshima, Miyazaki, and Kumamoto Prefectures, a total of 426 isolates from blood cultures were collected in the period from August, 1999 to February, 2000. Of these, 14 isolates (3.3%) were the species of Aeromonas. Of 14 isolates of Aeromonas, 13 were reported from Okinawa and the remaining one was from Kumamoto. Most patients had underlying diseases, particularly liver diseases including liver cirrhosis. The mortality rate was extremely high at 62.5%, and the patients died in short terms after blood culture became positive. With these, Aeromonas species infection is unique to Okinawa, and positive blood culture for Aeromonas species potentially indicates a high-risk, particularly among the patients with underlying diseases.