The goal of this study was to monitor 47 commercial swine herds at slaughter to determine Salmonella prevalence over a 2 year period. Mesenteric lymph nodes were collected (n=60, pooled 5:1 for a total of 12 samples) at the time of slaughter and cultured. Tissue samples were collected from the diaphragm and tested by ELISA. After a first phase of testing, we identified 10 herds that had both low culture positives and low average ELISA OD values. We also identified 10 herds that had both a high culture positives and high average ELISA OD values. The purpose of testing during Phase II was to see if the I 0 "low" herds remained low and the I 0 "high" herds remained high. The findings confirm the need for an on-going monitoring for tracking the changing Salmonella prevalence of swine herds over time.