We performed first-principles calculations on the ammonia (NH3) adsorption properties with zigzag and armchair single-walled BN nanotubes (SWBNNTs) using B3LYP/6-31G* basis set implemented in Gaussian 98 program. We considered the ammonia adsorption on structural and electronic properties of Al- and Ga-doped (8, 0), (5, 5) BNNTs. The adsorption energy for the most stable configuration of NH3 on Al-doped (8, 0) BNNT is about -0.182 eV, which is typical for the chemisorptions. We determined that both aluminum and gallium doping can significantly enhance the adsorption energy of NH3/BNNTs complexes. Our electronic results reveal that there is a significant orbital hybridization between two species in adsorption process being an evidence of covalent interaction. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.