The UV-Vis absorption spectra of some heterocyclic aromatic polymers were investigated with a combined theoretical and experimental approach. Geometry optimizations are performed with the semiempirical Austin Model (AM1) on PBZ (polybenzazole) oligomers with increasing chain length. Then the optical absorption spectra are simulated theoretically by using Zerner's intermediate neglect of differential overlap method (ZINDO), coupled to single configuration interaction (CI). The corresponding experimental spectra are recorded in MSA solution. The comparison of the observed and the calculated absorption spectra of PBZ show a deviation due to the effect of environment.