Aeromonas microorganisms normally grow at temperatures between 5 degrees C and 45 degrees C and therefore should have high thermotolerance. Thus it was of interest to find out whether A. hydrophila, A. caviae and A. veronii biovar sobria serovars respond to abrupt temperature changes with a heat shock-like response. To this end the present study was undertaken to determine whether Aeromonas species exhibits a heat shock response to different temperatures and time factors. The response of Aeromonas serovars to 24 h and 48 h of thermal stress at 25 degrees C, 42 degrees C and 50 degrees C involved the synthesis of 12-18 heat shock proteins (HSPs) bands with molecular weights ranging between 83.5-103.9 kDa in the high HSP molecular mass and 14.5-12.0 as low molecular mass HSP. Electrophoretic analysis of the HSPs showed that the serovars do not cluster very tightly and also that they are distinct from each other.