Previously we put forward a hypothesis about the role of FOXO-dependent mechanisms of stress-response gene activation after irradiation in radiation hormesis (Moskalev, 2008). To testify this assumption we analyze the influence of gamma-irradiation on duration of larvae development and imago lifespan in Drosophila strains with different FOXO function activity. We revealed that in FOXO hypomorphic allele homozygote strains the hormesis and adaptive response (increasing of larvae stage duration and longevity) were absent, in contrast to B wild type strain Canton-S and FOXO-heterozygotes.