A simple model for the calculation of HOMO and LUMO energy levels of benzocatafusenes (i.e., molecules that are only constituted by mutually condensed benzene rings and without interior carbon atoms, which belong to three benzene rings) is presented. Using semiempirical AM1 method, 615 benzocatafusenes were studied (29 normal and 586 branched). The relation between energy and molecular structure was coded by the three Huckel parameters: Coulomb integral, bond integral, and secular x eigenvalue. Analytical functions for HOMO and LUMO energy levels in terms of x parameter were obtained for normal benzocatafusenes, and energies for branched benzocatafusenes were satisfactorily modelled by the introduction of a simple correction function into the analytical functions describing normal benzocatafusenes. (C) 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2012