The mechanism of the reaction between H and CH₃NO₂, has been studied in a discharge flow system using electron paramagnetic resonance and modulated molecular beam mass spectrometry for the detection of reactants and products. Deuterium atoms have, in addition to CD₃NO₂, been used to support the proposed reaction mechanism. The reaction was studied with the atomic reactant in slight excess at 298 K and a total pressure of 2 Torr. Two concurrent reaction channels: (1a) H+CH₃NO₂→HONO+{radical dot}CH₃ and (1b) H+CH₃NO₂→CH₃NO+{radical dot}OH were observed. The branching ratio, k_1a/(k_1a+k_1b), is 0.7±0.2.