Completely resolved Doppler-free rotational line spectra of six vibronic two-photon bands in benzene C6 H6 and C6 D6 are presented. The excited final states possess different excess energies in S1 (1567 to 2727 cm−1 ) and are embedded in dense manifolds of background states with differing densities of states (1<rho<60 1/cm−1 ). The bands are analyzed by a statistical procedure. The intensity distribution of several hundreds of lines of each band is investigated. It is found that all weakly perturbed bands display a similar, peaked intensity distribution while in strongly perturbed bands the number of lines decreases monotonically with increasing intensity. The origin of this difference is discussed in terms of coupling to the many background states. The Journal of Chemical Physics is copyrighted by The American Institute of Physics.