The reactions of lithium and sodium aluminum hydride with alcs. and phenols in ether solvents were studied as a route to mono-, di- and triorganyloxyhydridoaluminates MAlH4-n(OR)n. However, the stability of these compds. towards disproportionation is strongly dependent on the steric demand of the org. group and the solvent. This process gives MAlH4 and more highly substituted organyloxyalumohydrides, as shown by 27Al NMR spectroscopy. The crystal structures of nine organyloxyhydridoaluminates were detd. by x-ray structure anal. Both Al-H-M and Al-O-M bridges were found for the coordination of the cation M (Li or Na). The species LiAlH3(OR) was stable only for R = 2,6-tBu2C6H3; it is dimeric in the solid state. Four stable solvated compds. MAlH2(OR)2 were obtained for M = Li, R = tBu2MeC (M = Li, Na), 2,6-tBu2C6H3 and M = Na, R = CPh3, all of which are mol. complexes in the solid state. Reductive ring opening of THF occurs for MAlH2(OC6H3tBu2-2,6)2 (M = Li, Na). Triorganyloxyhydridoaluminates are the most stable compds. in this series. For M = Li, R = tBu2MeC, CPh3, 2,6-iPr2C6H3 and M = Na, R = CPh3, crystal structures were detd. Depending on the bulk of the group R, both M-H-Al and M-O-Al bridges (smaller R groups) are obsd. [on SciFinder (R)]