Oxygen concentrations in the soil atmosphere greatly influenced the growth and mineral uptake of Eupatorium odoratum inoculated with Glomus macrocarpus. Shoot and root dry weights and length of mycorrhizal plants increased with O2 concentration up to 16%. Mycorrhizal plants at 21% O2 or non-aerated controls were smaller than those at 12 and 16% O2. Non-mycorrhizal plants had lower shoot and root dry wts than mycorrhizal plants at all O2 levels except at 0%. Phosphorus concentration in mycorrhizal and non-mycorrhizal plants differed significantly but did not increase with increasing O2. Mycorrhizal plants contained higher quantities of N, K, Ca and Mg than non-mycorrhizal and showed positive response in nutrient uptake to increase in soil O2. Inoculation and increased soil O2 resulted in higher concentrations of K and Mg but not of N and Ca. The development of Glomus macrocarpus exhibited quantitative and qualitative response to different soil O2 levels.