The thermolysis of the intramolecularly coordinated gallane [Me2N(CH2)(3)]GaMe2 (1) under various conditions has been investigated with matrix-isolation techniques (TR spectroscopy) and with mass spectroscopy (MS). The fragmentation of compound 1 begins above 600 degrees C; the IR and MS data are in agreement with a proposed P-hydrogen elimination reaction to give allyldimethylamine and dimethylgallane, Me2GaH. As deduced from the IR spectra of matrix-isolated species, the thermolysis mixtures contain the monomeric gallanes Me2GaH and MeGaH2, which have been identified with the help of ab initio and DFT calculations. The calculated frequencies [B3LYP/6-311 + G(2d,p) and MP2(fc)/6-311+G(7-d,p)] are compared with measured IR absorptions. The geometries of Me2GaH and MeGaH2 have been calculated using several methods [HF, MP2(fc), B3LYP] and basis sets [6-31G(d), 6-311G(d,p), 6-311 + G(2d,p)], and the results are discussed and compared with known literature data. Aside from the monomeric hydrides, the argon matrices of the thermolyses experiments contained CH4, HCN, H2C=CH2, H2C=C=CH2, H2C=NMe, [H2CCHCH2](.), H2C=CHCH3, HX, and MeGa. Whereas the carbon-containing species have been identified by comparison with known literature data, methylgallium(I), well-known from mass spectroscopy, was characterized for the first time by IR spectroscopy as a matrix-isolated species. The experimental vibrational frequencies of GaMe are compared with harmonic frequencies calculated at several levels of theory.