The effect of increased carbon dioxide concentration in atmosphere was examined on the pheromone system of Helicoverpa armigera reared from egg stage to adult in three room. Two of three room (2×2×2 m) were treated with carbon dioxide gas as 600 ppm and 1,000 ppm, respectively. Mean of carbon dioxide concentration was 429.1 ppm in the control, 603.3 ppm for 600 ppm, and 1011.5 ppm for 1,000 ppm during experiment. Electroantenograph (EAG) test was conducted on 3-d-old male adults with air, hexane, and a series of their sex pheromone component, Z11-16Al, from 0.01 to 100 ng. The result was that male EAG responses of 600 and 1,000 ppm were 30.3% lower than that of control room. Production of Z11-16:Al was examined on about twenty 2-d-old virgin females. Carbon dioxide increases did not show a statistically significant difference. However, higher amount of sex pheromone was produced in females of 600 and 1,000 ppm. So, This experiment was replicated with different population reared again. The amount of the sex pheromone per female was 108.9 and 118.1 ng in control room, 139.8 and 141.8 ng in 600 ppm room, and 124.6 and 125.8 ng in 1,000 ppm room.