Summary: A total of 1568 chicks from five breeds and strains of the fowl, and of one group consisting of hybrids between two of the breeds, were injected in the same way with a standard dosage of virulent fowl typhoid bacteria. The percentage mortalities observed for the various breeds were: White Plymouth Rock, 79.7; White Leghorn, 87.7; White Leghorn II, 86.3; White Wyandotte, 93.4; Rhode Island Red, 94.4; and for hybrids between the White Leghorn and Rhode Island Red, 86.4 A number of these differences are greater than would be expected from random sampling. Differences in the rate of mortality also were observed for the different breeds. Significant differences in resistance were not observed between the chicks from separate colony matings, one male with several females, in one strain of the White Leghorn breed.