Eggs of Japanese quail (Coturnix coturnix japonica) were irradiated before incubation with doses of 300, 500, 800, 1500, 2000 and 2500 R of /sup 60/Co gamma rays at a dose rate of 187 R/min. The parameters of hatchability, embryonic morphology in the last phases of development, growth changes, viability, sex ratio and production of eggs in the control and experimental groups were followed. Embryonic mortality was proportional to the dose, irradiation weakened the embryos, at doses of 800 R and more the radiation evoked various teratogenic changes and slightly lengthened the incubation period. For the period of embryonic development, LD/sub 50/ approximately equal to 800 R and LD/sub 100/=2500 R was determined. Radiation slightly suppressed growth, viability in the postembryonic stage was influenced very slightly. Irradiation of eggs did not influence the sex ratio; the production of eggs was significantly reduced only at a dose of 1500 R and more.