Ab initio calculations using a Gaussian orbital basis set were performed on the two boron-nitrogen polymer systems polyaminoborane and polyboronimide. For the polyaminoborane system an alternating B-N bond model appears to be more stable than a symmetric B-N bond model. An electron drift from the NH2 group to the BH2 moiety was calculated for both models although the nitrogen atom was found to possess a negative charge stemming from polarization of the N-H bonds. The energy band diagrams derived from both models show rather featureless bands indicative of weakly interactive systems although that of polyboronimide indicates that it is a more delocalized system than its saturated counterpart. The conduction and valence bands at the X-point are composed of π orbitals and the lowest electronic transition is predicted to be π—π* in nature. The electron distribution of polyboronimide indicates a movement of σ-electrons from the boron to the nitrogen coupled with a smaller π-electron drift from the nitrogen to the boron.