An ab initio-based global double many-body expansion potential energy surface is reported for the first electronic state of the NO2((2)A '') manifold. Up to 1700 ab initio energies have been employed to map the full configuration space of the title molecule, including stationary points and asymptotic channels. The calculated grid energies have been scaled to account for the incompleteness of the basis set and truncation of the MRCI expansion and fitted analytically with a total root-mean-squared-deviation smaller than 1.0 kcal mol(-1). The lowest point of the potential energy surface corresponds to the B-2(1) linear minimum, which is separated from the C-s distorted minimum by a C-2 nu barrier of approximate to 9.7 kcal mol(-1). As usual, the proposed form includes a realistic representation of long-range interactions. Preliminary work indicates its reliability for reaction dynamics.