Two lots of laboratory pasteurized cooking butter artificially contaminated with approx. 10 Aeromonas hydrophila/g were prepared. The first lot was stored at refrigerator temperature while, the other at freezing temperature. Samples were taken and examined initially, after 24 h and then weekly up to six weeks for pH value and number of A. hydrophila/g. More reduction in the counts of the organism occured during freezing storage than refrigerator storage. A. hydrophila survived 6 weeks at pH 4.6. The public health significance of these findings is discussed.