The dissociation rate of benzene and d(6)-benzene were measured under collision-free condition by multimass ion imaging techniques. The value of 1 +/- 0.2x10(5) s(-1) and 5 +/-1x10(4) s(-1) were obtained for benzene and d(6)-benzene, respectively, with internal energy of 618 kJ/mol. The dissociation rate of benzene with internal energy of 483 kJ/mol was too slow to be measured, and the upper limit of the dissociation rate was estimated to be 3x10(3) s(-1).