Collisional energy transfer from large, highly vibrationally excited molecules has been studied by quasiclassical trajectory calculations and results for large polyatomic colliders are reported for the first time. Highly excited benzene molecules in a thermal bath gas of benzene were investigated using a sum of atom-atom Lennard-Jones interactions for the intermolecular potential. Excellent agreement with experiment has been found for the first moment of energy transfer [Delta E] and its energy dependence. [Delta E] is increasing with a slight leveling off at high energies. The results suggest that vibrational energy loss of the excited molecule is dominated by V-V transfer.