The NH3/NO2 system has been investigated experimentally in an isothermal flow reactor in the temperature range 850-1350 X. The experimental data were interpreted in terms of a detailed reaction mechanism. The flow reactor results, supported by a theoretical analysis of the NH2-NO2 complex, suggest that the NH2 + NO2 reaction has two major product channels, both proceeding without activation barriers:(R20) NH2 reversible arrow N2O + H2O(R20) NH2 reversible arrow H2NO + NOOur findings indicate that the N2O + H2O channel is dominant at low temperatures while H2NO + NO dominates at high temperatures. The rate constant for reaction (R21) is estimated to be 3.5 . 10(12) cm(3)/mol-s in the temperature range studied with an uncertainty of a factor of 3.