The heats of formation of four C2H3N molecules and the three most stable C2H2N cations, namely, cyanomethyl, isocyanomethyl, and azirinyl, together with their corresponding radicals and anions, have been calculated at the G2, G2(//QCI), CBS-Q, and CBS-RAD levels of theory. In addition, bond dissociation enthalpies and gas-phase acidities of the molecules and the electron affinities and ionization energies of the free radicals have been derived. Comparison of the theoretical results with available experimental values shows generally good agreement with directly measured experimental data but significant discrepancies in several instances for derived quantities.