HIGH density housing utilizing wire floors has been shown to have application for commercial layers (Bressler, 1961, and Bressler and Maw, 1966). In preliminary experiments, Bressler et al. (1967) demonstrated the feasibility of maintaining Leghorn breeders at high density on wire floors without encountering fertility or hatchability problems. Eggs from flocks on wire routinely had less gross bacterial contamination than eggs from conventional litter floor houses.Previous studies on egg shell contamination have employed inoculation of the shell bacterial cultures and their subsequent recovery from the egg contents. McNally (1954) reported a significant correlation between bacterial penetration of the shell and the temperature and humidity during storage. Graves and McLaury (1962) showed that in addition to temperature and humidity, vapor pressure also had significant correlation with bacterial penetration. The mechanism of shell penetration of Salmonella has been studied by Williams and Whitemore (1967).Gross contamination of the egg shell with…