The novel compounds (MeNHGaH2)n and (MeNHGaD2)n have been prepared, and their physical and chemical properties investigated. They are trimeric in benzene solution, and 1H n.m.r. studies show the presence of two isomers for the six-membered (Ga–N)3 ring, which is considered to be in the chair conformation. Aminogallane, (H2NGaH2)n, was formed as a polymeric material, insoluble in organic solvents. N.m.r. of the related organogallanes, (Me2NGaMe2)n and (MeNHGaMe2)n, has been studied in an attempt to elucidate the factors which govern the degree of association of this type of Ga–N system. Similar reactions involving trimethylamine-alane, Me3N,AlH3, have been investigated, and a comparison is made between the compounds studied in this work and similar boron systems.