Two cultivars Deltapins 50 and 90 (G. hirsutum, L.) grown under field conditions in open-top chambers were subjected to chronic combinations (2 levels each) of climatic factors soil moisture (-0.05 and -0.1 MPa), CO₂ (ambient and 500 µmol CO₂ mol^-1), and O₃ [carbon-filtered (CF) and non-filtered (NF) air]. The average NF air (45.3 nmol O₃ mol^-1) concentration during the growing season showed no visible O₃-injury. The combinations of O₃ and CO₂ treatment interactive effects indicated that NF+350 µmol CO₂ mol^-1 and CF+500 µmol CO₂ mol^-1 had higher seedcotton and lint yield (20 to 30%) under both W and D conditions. Positive effects of CO₂ enrichment on physiological and morphological characteristics appeared to have no effect on yield, except for plants treated with CF air under both soil moisture levels had improved yield. The results suggest that treatments inducing higher photosynthesis, morphological growth, and biomass accumulation do not necessarily result in higher yields. DP50 showed 20 - 34% higher yield than DP90, which could be attributed to its superior physiological, morphological and reproductive characteristics.