A calculation of the intermediate scattering function of an entangled melt of asymmetric diblock copolymers is presented. On the basis of the reptation model of polymer dynamics and the dynamic random phase approximation, it is shown that the spectrum of relaxation rates for an asymmetric diblock copolymer consists of two sets of modes. In the noninteracting case, both sets of modes have relaxation rates that are independent of the diblock composition. The relative mode amplitudes, however, depend strongly on composition. In the noninteracting case, one set has relaxation rates given by Gamma(p,beta) = beta(p)(2)/t*, with 4t* the disengagement time and beta(p) given by the pth positive root of beta(p) cot beta(p) - (qR(g))(2)/2 = 0, p = 1, 2, 3,.... The other set only appears in the asymmetric case, and, in both the small-qR(g) and large-qR(g) limits, has relaxation rates given by Gamma(p,alpha) = (pi(2)/4t*)(2p - 2)(2), p = 2, 3, 4,....