The Aeromonas species rarely produce human infection but in the cases of concomitant hepatobiliary lesion or leukemia, it invades as opportunistic infection and easily develops to septicemia. Occasionally ecthyma gangrenosum-like skin lesion is associated with Aeromonas septicemia. Since 1981, we have experienced 5 cases of Aeromonas septicemia which were confirmed by blood cultures. The following is the summary of the general features of Aeromonas septicemia. 1) All 5 cases revealed positive blood cultures. 1 case of cholecystitis with multiple stones was positive in bile culture. 2) Among 5 cases, 4 cases were man and all were above forty years. In 4 cases the outbreak was happened during July and August. 3) All patients had associated hepatobiliary disorders and 3 cases were fatal. 4) Recent 3 cases showed skin lesions, purplish deep seated hematomas, on the both lower extremities, seen as ecthyma gangrenosum-like lesion produced by Ps. aeruginosa. 5) The Aeromonas species were sensitive to chloramphenicol, gentamicin, kanamycin, tetracycline, tobramycin, cephalothin and cefoperazone, but resistant to ampicillin.