The influence of antisite defects in InN is analyzed theoretically using a Linear Combination of Atomic Orbitals approach. The procedure used is validated by confirming the band gaps of common binary alloy semiconductor materials. InN with N-In and In-N antisite defects are then analyzed and it is found that in the case of InN:N-In, the excess nitrogen acts as a donor species with its level resident in the conduction band. For InN:In-N, it is Shown that when there is a significant density of the excess indium present as the antisite defect, tunnel optical absorption should occur in the infrared at 0.2 eV. (c) 2005 Elsevier B.V. All rights reserved.