Preliminary incubation (P. I.) encourages the growth of bacterial contaminants, and aids in detecting milks where good cooling masks insanitary production or handling practices. Evidence is submitted to show the superiority of 55°F. for 18 hours for P. I. Using this procedure, a standard plate count of 200,000/ml. is suggested as a desirable standard to aim for. This would serve to emphasize thorough cleaning along with efficient cooling in the production of quality milk.