Technical Abstract: The use of monosex populations for aquaculture is becoming widely used for several species. Monosex populations are not in wide use in the catfish industry but techniques to develop all male populations have been developed. These studies were conducted to determine if there were any differences between male and female channel catfish, Ictalurus punctatus, in disease susceptibility to Edwardsiella ictaluri, one of the most important pathogenic bacteria in catfish culture. Disease challenge experiments were done on fingerling channel catfish fed 17ß-estradiol or testosterone before the challenge, and on all male and on sibling all female fingerlings. The all male populations were produced by mating YY males with normal XX females. Sibling females were produced by hormonally sex-reversing a sub-population of six of the all male families. Weight gain or specific growth rate did not differ in fish fed testosterone or estrogen. Fish fed the highest dose of estrogen (50 mg/kg) had a significant higher mortality (P < 0.05), while mortality was similar in catfish fed 10 and 50 mg/kg of testosterone compared, to controls. There were no differences in mortality between sibling males and females. These data indicate no increased disease susceptibility to E. ictaluri between males and females or due to exogenous sex hormones. Production of all male catfish for culture can proceed without concern for disease susceptibility to E. ictaluri.