Effects of exposing quail eggs to high temperature on the heat tolerance ability and productivity of birds were investigated. Four groups of 600 fertile eggs were randomly selected; the first group was incubated under 37.5 °C and the hatched chicks were reared under a gradual decrease in temperature from 35 to 24 °C (Control). The second group was exposed to 39.1 °C for 2 h/day during 4–14 days of embryogenesis and the hatched chicks were reared under a gradual decrease in temperature from 35 to 24 °C. The third group was incubated under 37.5 °C and the hatched chicks were exposed to 39 ± 1 °C for 2 h/day during 4–14 days of age. The fourth group was exposed to 39 ± 1 °C for 2 h during 4–14 days of embryogenesis and the hatched chicks were exposed to 39 ± 1 °C for 2 h/day during 4–14 days of age. The temperature applied changed (P < 0.01) embryo weight and incubation period