The steps in Grade A production of bovine milk for human consumption were assessed. A cumulative distribution of values, based on published data, was used to evaluate steps for milking, storage, transportation and pasteurization. Conservative estimates of parameters in the distributions were used to compute concentrations and probabilities. Under normal operations, the probability was less than 2 in 100 that one Listeria monocytogenes cell occurs in every 2 gallons of milk processed at exactly 71.7°C for 15 s. The probability was less than 2 in 100 that one cell occurs in 3.8 × 1010 gallons processed at 74.4°C for 20 s.