Two experiments were conducted to evaluate the effect of ascorbic acid (AA) during egg incubation on development of broiler chickens of a commercial stock. In Experiment ١, eggs with living embryos were injected at ١٥ d of incubation with ٠٫١ ml of saline solution containing either ٣ or ١٢ mg of AA per egg and uninjected control. Body weights of each treatment were determined weekly from hatch to ٦ wk of age. In Experiment ٢, the treatments at ١٥ d of incubation were as follows: ١) eggs injected with ٣ mg of AA and then cooled at ٢٢° C for ٢٤ h; ٢) eggs dipped in ٣٪ solution of AA for ٣ min and then cooled at ٢٢° C for ٢٤ h; and ٣) control. Embryo weight at ١٩ d of incubation, hatchability and body weights of the hatched chicks were determined.