The AlCH 3 molecule has been observed by both neutralization-reionization mass spectrometry (NRMS) and resonance-enhanced multiphoton spectroscopy (REMPI), and GaCH 3 is a target molecule for both experimental techniques. Ab initio quantum mechanical methods have accordingly been applied to GaCH 3. GaCH 3 is predicted to have a C 3 v equilibrium geometry, and theoretical values of its rotational constants, vibrational frequencies and infrared intensities are presented.