A five-parameter nonlinear model is introduced to the description of the stretching vibrational modes of benzenemolecule in the electronic ground state, and is applied for the first time to the calculations of energy levels of C-H andC-D stretches of C6H6 and C6D6 in vapor phase. The results obtained agree well with the experimental vibrationalenergy levels and with the results obtained from other model calculations. Moreover, our model calculations predictaccurately some new overtone and combination bands that have not been studied experimentally.