Thermal rearrangement reactions of (aminomethyl) silane H3SiCH2NH2 were studied by ab initio calculations at the G3 level. The results show that two dyotropic reactions could happen when H3SiCH2NH2 is heated. In one reaction, the silyl group migrates from the carbon to the nitrogen atom while a hydrogen atom shifts from the nitrogen to the carbon atom, forming (methylamino) silane CH3NHSiH3 (reaction A). This reaction can proceed via three paths: a path involving two consecutive steps with two transition states and one intermediate metastable carbene species (A-1); and two concerted paths (A-2 and A-3). In the other reaction, the amino group migrates from the carbon to the silicon atom while a hydrogen atom shifts from the silicon to the carbon atom, via a double three-membered ring transition state, forming aminomethylsilane CH3SiH2NH2 (reaction B). Reaction rate constants, changes (Delta S-double dagger, Delta H, and Delta G) in thermodynamic functions and equilibrium constants of the reactions were calculated with the MP2(full)/6-311G(d,p) optimized geometries, harmonic vibrational frequencies and G3 energies of reactants, transition states, intermediates and products with statistical mechanical methods and the conventional transition-state theory (TST) with Wigner tunneling approximation over a temperature range 400-1800 K.