The ability of 15 Aeromonas sobria and 9 Aeromonas hydrophila isolates to cause subcutaneous lesions was tested. An inoculum of 10(11) colony forming units/l was injected subcutaneously into mice. Surviving animals developed a subcutaneous abscess and/or localised skin sloughing and loss of hair (alopecia). An abscess was induced by all nine A. hydrophila isolates and by three of the 15 A. sobria isolates. The induction of local epidermal sloughing and loss of hair followed challenge with either A. hydrophila or A. sobria and correlated with the organisms' lethality for mice and their cytotoxicity in the Y-I adrenal cell assay. Local epidermal sloughing was not induced by the media used for growing the organisms or by sonicated cells of the isolates. The ability to cause epidermal sloughing was lost by incubating viable cells at 45 degrees C for 35 minutes. These yet unreported in vivo features of Aeromonas sp. may be useful in studies of the pathogenicity of the species as well as for rapid assay of toxicity of strains.