Abstract With the introduction of aureomycin supplements in poultry growing mashes, it is of interest to note whether this antibiotic, when fed to laying birds, has any influence on egg quality factors. Observations on blood and meat spot incidence are of particular interest because of the controversy surrounding the effect of aureomycin on clotting time of blood (Macht and Farkas, 1949; Parker and Wright, 1952). For this study, size and incidence of blood and meat spots, shell thickness, egg weight, and albumen quality were observed in eggs from hens fed various levels of aureomycin. Egg samples were taken in April and November of the same year. At twenty-two weeks of age two hundred and forty March hatched Rhode Island Red pullets were transferred from range to six houses with forty birds in each. The first egg sample was taken when the birds were twelve months of age and had been housed …