The a priori predicted vibrational spectra of fluorene and newly synthesized methylene bridged planarized poly(p-phenylene)(PPP) are presented. The calculated vibrational frequencies of fluorene are compared to those obtained experimentally to resolve differences between earlier experiments. As a result, some reassignments are made. The vibrational spectra of planarized PPP are extrapolated using oligomers as a starting point within the scaled quantum mechanical oligomer force field (SQMOFF) method.; The basis get used is split valence double-zeta quality 3-21G. The scaling factors are transferred from benzene and cyclopentadiene as fixed parameters in the polymer calculations. Planarized PPP is predicted to have an inter-ring stretching frequency of 1338 cm(-1), an upward shift as compared to that of PPP (about 1280 cm(-1) experimental value). This shift is largely attributed to the increase in the rigidity of the polymer backbone due to the presence of the bridging group. This frequency shift is also indicative of a higher degree of conjugation due to the planar conformation of methylene bridged PPP. The predicted Raman intensity ratio of the A, modes is compared to that predicted by the effective conjugation coordinate (ECC) theory. Because of the presence of the bridging methylene group, the predictive power of the ECC theory is limited. The predicted IR spectrum shows a strong peak at 844 cm(-1), a characteristic C-H out-of-plane bending frequency of a 1,2,4,5-tetrasubstituted phenyl ring. Besides the three new bands originating from the CH2 bridge, we predict two more strong skeletal bands, at 1440 and 1351 cm(-1), in the IR spectrum of planarized PPP.