A SIGNIFICANT pre-hatching alteration of the sex-ratio in poultry would have tremendous impact upon the industry. An increase in percentage of eggs which hatch into functional females would be worth thousands of dollars to hatcheries producing egg-laying stocks. On the other hand, an increase in males would provide faster growing broilers, turkeys and waterfowl, for meat production.In 1963 a preliminary study of the effect of gamma radiation on the developing embryo produced a high incidence of males from eggs which were treated on the ninth day of incubation (Morgan and Whitehead, 1964). Subsequent exposure of 480 eggs in a later trial, resulted in a hatch of 215 males and 174 females (Morgan, 1966), a departure which is significant at the 5% level from the theoretically expected 50:50 ratio. Inasmuch as the altered ratio was not associated with exposure in the latter study, another experiment was specifically designed to determine .