DURING the three-year period, 1946–1948 inclusive, 14 strains of Single Comb White Leghorns were obtained from prominent Leghorn breeders and brought to the Alabama Agricultural Experiment Station Poultry Farm for comparative performance tests with a resistant strain of White Leghorns that was developed at this station (Sturkie, 1943; King and Cottier, 1948; Moultrie et al., 1953). Following the 1948 test, one of the introduced strains that was superior in egg production and other economic traits and about average in livability at this station was chosen for crossing with the resistant strain for the purpose of studying the performance of F1 inter-strain hybrids produced from non-inbred stock.The results obtained from crossing these two strains for three consecutive years provide evidence that both heterosis and maternal effects play roles in determining viability of the inter-strain hybrids. Presentation of this evidence is the object of this report.MATERIALS AND METHODSStrain A, …