A set of 37 strains including 13 serotypes of Listeria monocytogenes (Lm) were analyzed for heat tolerance at 60°C for 10 min and further categorized into three groups; low (strains with <2 log survival), medium (2-4 log survival), and high (4-6 log survival) heat tolerant. When Lm strains representing each group were subjected to sub-lethal heatstress at 48°C prior to 60°C, the survivals of all strains were increased by at least 5 log CFU/ml when compared to controls. Sub-lethal heat-stress at 48°C for 30-60 min increased the heat-stress resistance of Lm strains by doubling D60°C values from 1.9-4.3 to 5.0-10.4 min. When Lm cells were cooled after sublethal heat-stress at 48°C prior to 60°C treatment, such acquired heat-stress adaptation was unstable at 22°C but was found to be highly stable for up to 24 h at 4°C. These results will have potential implications in food safety risk analysis for Lm.