Abstract: The effect of genotype on postnatal efficiencies of chickens has been well documented. However, little is known about the effect of genotype on body composition and metabolic physiology of chickens during embryonic development. To test the hypothesis that even with equalised egg weight at setting during incubation, there could be some effect of genotype on body composition, an experiment was conducted with embryonic chicks of broiler and layer genotypes at four stages of development during incubation (viz. 12, 16, 18, 20th d). Wet weight (P<0.01) and dry weight (P<0.05) of embryos were higher in broilers compared to layers. Irrespective of genotype, the wet and dry weights increased (P<0.01) progressively and significantly from day 12 to day 20. Water content was not found to be affected by genotype but goes progressively down till 20th d of incubation. Body nitrogen concentration was higher (P<0.05) in the pre-hatch chicks of broiler vs. layer genotype but stage of development did not significantly influence the value of this parameter. Broiler had higher (P<0.05) ether extract than layer prehatch chicks. Ether extract increased progressively and significantly (P<0.01) during the entire period of pre-hatch development. Body ash content was neither affected by genotype nor stage of development during embryonic period. This appears to be the first report that demonstrates differences in the body composition of broiler and layer genotype during embryonic life life itself.