Two-year-old Betula platyphylla Sukatchev var. japonica, three-year-old Betula ermanii Cham., four-year-old Fagus crenata Blume, two-year-old Pinus densiflora Sieb. Et Zucc. And Cryptomeria japonica D. Don seedling were exposed to ambient or elevated ozone (O₃) and carbon dioxide (CO₂) during two growing seasons (from 12 July to 31 October in 2002 and from 26 March to 31 October in 2003) in Gunma, Japan. Ten open-top chambers were used for five different treatments: filtered air, ambient air (1.0x ambient O₃), elevated O₃ (1.5x ambient), elevated CO₂ (1.5x ambient), and elevated O₃ and CO₂ combined. At ambient CO₂ concentration, growth of all five tree species examined significantly decreased with increasing level of O₃. On the other hand, growth of all five tree species in elevated CO₂ treatment significantly increased as compared with ambient air treatment. Significant interactions between O₃ and CO₂ treatment could not be found on the growth parameters of B. ermanii, F. crenata, P. densiflora and C. japonica but on that of B. platyphylla. Elevated CO₂ effect on O₃- induced growth depression was counteractive on B. platyphylla while not on the other four tree species. Results indicate that responses to elevated O₃ and CO₂ of growth are species specific.