We present the results of a preliminary study of the quartet states of the complex formed between the ground-state NO ((XII)-I-2) and the ground-state O-2 (X(3)Sigma (-)(g)) molecules. Geometry optimizations are performed at the UQCISD/6-31+G* and UQCISD/6-311+G(2d) level. Binding energies are then calculated for the three lowest energy isomers at the RCCSD(T)/aug-cc-pVQZ level. The lowest energy isomer is found to be a T-shaped C-2v NO(O-2) structure, with a D-e value of similar to 110 cm(-1), after correction for BSSE. The favoured geometry seems to suggest that electron repulsion is an important consideration in this species.