Fertile avian eggs from the domestic fowl and the Japan quail showed a measurable loss of weight and a reduction atchability when exposed to varying intensities of centrifugal force for 10 min. Both of these effects are proportional to intensity of the applied force. Coturnix (Japanese quail) chicks hatched from eggs exposed to centrifugal forces prior to incubation displayed no growth rate differences from those chicks from control eggs. Impact force necessary to cause failure of embryo development is in excess of shell failure stress. The effect of subacute acceleration and impact deceleration is not manifested in the same manner in embryonated as in fertile eggs. mechanical force; impact deceleration; centrifugal force; avian eggs; hatchability; embryo development Submitted on December 31, 1964