The calculated proton affinities of four borane-amines using Gaussian-2 theory have been found to be comparable to conventional bases such as water, methanol, and ammonia. On the other hand the structure of protonated borane-ammonia, [HBH3-NH3](+), is found to be drastically different from that of protonated ammonia, [HNH3](+), and can appropriately be described as a eta(2)-H-2 complex with [BH2-NH3](+) molecular cation. Further, the proton affinities of borane-amines are related to the ease of H-2 elimination.