The effect of High-Pressure Homogenization treatments at 150MPa on the viability of microbial flora in natural and spiked brines for cheesemaking was assessed. The microbial reductions increased with the number of passes through the homogenization valve (with or without temperature control) and this behavior was well described by a linear equation. Higher microbial reduction rates were observed when temperature was not controlled during processing. In this case, temperature progressively increased because of HPH process up to 75 degrees C after 11 passes. The killing effect of HPH treatments was caused by the synergic action of physical and mechanical stresses suffered by the product during the passage through the homogenization valve. These effects were further enlarged when temperature increased as number of passes also increased. The HPH treatments allowed an almost total inactivation of most of the native contaminants just after 5 passages, and the same treatment was effective against potentially pathogenic and spoilage microorganisms in the spiked brines, causing the total inactivation of L. monocytogenes.