Ab initio molecular orbital calculations at the G2(MP2,SVP) level have been employed to explore a large part of the [H-3, C, N, O](.+) potential energy surface. Ionized aminohydroxycarbene, NH2-C.+-OH, 1, is found to correspond to the global minimum of the surface. The other stable species are also unconventional structures: ion-neutral complexes OC . . . NH3+., 2 and CO . . . NH3+., 2', and the distonic ion, (H3N+CO)-O-., 3. The more classical structures [HCONH2](.+), 4, and [HC(OH)NH](.+), 5 are higher in energy. The heat of formation of the five radical cations have been determined using their atomization energies. The various isomerization reactions connecting 1-5 as well as their dissociation by H or CO losses have been theoretically investigated and compared with the available experimental data.