The dimethylcarbene radical cation, (CH3)(2)C.+, has been generated in the gas phase. Experimental identification was achieved by charge stripping mass spectrometry whereby the stable dimethylcarbene dication, (CK3)(2)C2+, is observed. Electron impact appearance energy measurements and G2 ab initio molecular orbital calculations have been used to investigate the thermochemistry of the dimethylcarbene radical cation. The carbene radical cation is calculated to lie 84 kJ mol(-1) above the propene radical cation and to be separated from it by a barrier of 35 kJ mol(-1).