Dissociative electron attachment (DEA) to CH3NO2 in the gas phase was studied in the electron energy range from zero up to 10 eV with an energy resolution of 140 meV. For the most intense negative fragments NO2-, O-, OH-, CN-, CNO- estimates for the absolute partial cross sections were obtained for the first time [sigma(NO2)approximate to10(-21) m(2) at 0.62 eV, sigma(O-)approximate to10(-23) m(2) at 5.4 eV, sigma(OH-)approximate to10(-24) m(2) at 4 eV, sigma(CN-)approximate to10(-24) m(2) at 1.7 eV, and sigma(CNO-)approximate to10(-25) m(2) at 4 eV]. In the case of OH-, CN-, and CNO-, ion formation at very low electron energies (approximate to0 eV) has been observed in contrast to previous studies. The formation of OH-and CNO- at these low electron energies is explained in terms of DEA to vibrationally excited molecules. Analyzing measured partial cross sections, the standard enthalpy of formation of the CH3NO (nitroso-methane) and the CNO radical has been estimated, as Delta(f)H(g)(o)(CH3NO)=129+/-30 kJ/mol and Delta(f)H(g)(o)(CNO)=323+/-30 kJ/mol, respectively.