The thermochemistry of dissociation and elimination reactions of organogallium precursors for the GaN chemical vapor deposition (CVD) is studied at the hybrid Hartree-Foc/density functional level of theory (B3LYP/pVDZ). Geometries, relative energies, vibrational frequencies of RxGaNR ' (x) species, and their dissociation products (NRx, GaRx, x = 1-3; (R, R ' = H, CH3)) are presented. Methane elimination from the source adducts is exothermic at standard conditions, while hydrogen elimination is endothermic. Both for R = H, CH3 elimination reactions are predicted to be more favorable compared to dissociation into components, in contrast to the halogen containing precursors, The Ga-N bond dissociation enthalpies (kJ mol(-1)) are the highest for R2GaNR ' (2) compounds (313-382), followed by RGaNR ' (196-266); and for donor-acceptor complexes R3GaNR ' (3) (56-100) they are the lowest. (CH3)(x)GaNHx isomers are more than 50 kJ mol(-1) lower in energy than H,GaN(CH3), species, but the formation of Ga-H and N-H bonds is the thermodynamically most favorable process. Hence, the replacement of alkyl groups might be viable during the CVD process from trimethylgallium and ammonia.