A study was undertaken to discriminate the strains of Aeromonas hydrophila isolated from fi sh and diarrhoeal samples by SDS-PAGE analysis of outer membrane proteins (OMPs) and lipopolysaccharides (LPSs). Common bands at 47 kDa positions for OMPs and at 31-38 kDa for LPSs were observed. No strain of A. hydrophila from clinical or fi sh samples was found identical in either OMPs or LPSs profi le.