Alane (AlH3) has attracted much recent attention for various energy related applications. Amines are commonly used as stabilization agents in alane complexes, with N-methylpyrrolidine (NMP) in particular for favorable properties. However, there have been complications in the study of alane−NMP complexes due to the fact that the widely employed synthesis schemes would produce a mixture of complexes in different compositions. Reported here are the preparation and quantitative characterization of two complexes AlH3·NMP and AlH3·(NMP)2, and also AlH2Cl·(NMP)2 as a product obtained under slightly different reaction conditions. Results on the hydrogen storage capacities in and hydrogen release from these complexes are also reported and discussed.