Aeromonas spp. were isolated from blood cultures taken from four clinically bacteraemic patients over an 18 day period on four separate wards. A common source was suspected and extensive environmental sampling revealed two more ward isolates of Aeromonas spp. A biotyping system was employed which distinguished the strains from each other and indicated that a common source was unlikely. This coincidental clustering occurred in the autumn, a period when isolates from water and faeces are normally at a peak. All patients were debilitated and it is postulated that their own gastrointestinal tracts acted as the most likely route for their bacteraemias.