The presence of vibrational excitons in liquid benzene has been tested by the method of isotopic dilution. A C6H6/C6D6 concentration study on the infrared and Raman fundamental modes reveals that the umbrella (A 2u ) vibrational exciton in solid benzene retains its characteristics upon melting and at room temperature. The total liquidexciton bandwidth is about 40 cm−1, practically the same as in the solid. This indicates an instantaneous local liquid structure similar to that of the solid (the C i crystal site symmetry is also nearly preserved), in general agreement with indications from other methods. The fastest nearest neighbor vibrational resonant transfer takes about 1 psec. The residual linewidth at isotopic dilution is 3–4 cm−1, which is due to inhomogeneous and/or homogeneous broadening. The respective overall reorientational and/or translational relaxation takes about 2 psec o r l o n g e r. The excitonlinewidth is proportional to the square root of the isotopic concentration except for a sudden break at some critical concentration.