Technical Abstract: Though egg shell microbiology has been studied extensively, only a handful of studies describe how modern U.S. processing conditions impact microbial populations. As regulations are being drafted for the industry, such information can be important in determining processing steps that are critical to product safety. Five different shell egg surface populations (aerobic, yeasts/molds, Enterobacteriaceae, Escherichia coli, and Salmonella) were monitored at twelve points along the processing line (accumulator, pre-wash rinse, washer one, washer two, sanitizer, dryer, oiler, scales, two packer head lanes, re-wash entrance, re-wash exit). Three commercial facilities were each visited three times allowing for the sampling of 990 eggs and subsequently analyzed by 5,220 microbiological samples. Though variations existed in levels of microorganisms recovered from plant to plant, the patterns of fluctuations for each population were similar at each plant. On average, aerobes, yeasts/molds, Enterobacteriaceae, and E. coli prevalence were reduced by 30%, 20%, 50% and 30%, respectively, by end of processing. Log10 CFU/ml rinse on eggs collected from packer head lanes were decreased by 3.3, 1.3, 1.3, and 0.5, respectively, when compared to rinses from eggs collected at the accumulator. Salmonella was recovered from 0'48% of pooled samples in the three repetitions. More Salmonella was recovered from pre-processed than in-process or ready to pack eggs. These data demonstrate that current commercial practices decrease microbial contamination of egg shell surfaces.