The structural and electronic properties of armchair and zigzag models of single-wall BN nanotubes have been investigated by performing semi-empirical molecular orbital self-consistent field calculations at the level of the Austin Model 1 (AM1) method within the RHF formulation. It has been found that these structures are stable and exothermic. The armchair model has a zero net dipole moment, whereas the zigzag model has a nonzero net dipole moment. The interfrontier molecular energy gap of these systems are close to each other, thus the gap is independent of the chirality of the tube. (C) 2001 Elsevier Science B.V. All rights reserved.