For a series of cis-polyisoprene (PI) chains having almost identical molecular weights (M congruent-to 48K) but differently inverted type-A dipoles parallel along the chain contour, dielectric relaxation behavior was examined in homogeneous blends with a polybutadiene matrix (B-9; M = 9K). In the blends, the PI chains were dilute and entangled only with the shorter B-9 matrix. This matrix was dielectrically inert, and the dielectric loss (epsilon") of the blends was attributed to global motion of the PI chains having type-A dipoles. Because of the differences of the location of the dipole inversion points, the PI chains of almost identical M exhibited remarkably different epsilon" curves. As the inversion point shifted from the chain end to the center, the curve shifted to the higher frequency (omega) side and the relaxation mode distribution became first broader and then narrow again. Those PI chains relaxed locally as the shorter matrix B-9 chains rapidly diffused away and globally by accumulating such local processes. For this type of relaxation generally referred to as constraint release (CR) relaxation, the epsilon" data enabled us to evaluate low-order eigenfunctions f(p)(n) (with the mode number p = 1-3) for a local correlation function, C(n,t;m) = (1/a2)[u(n,t).u(m,0)] (u(n,t) = nth bond vector at time t and a2 = [u2]). Those f(p)(n) were not largely but certainly different from sinusoidal eigenfunctions f(p)degrees(n) deduced from a conventional CR model assuming Rouse nature of CR processes. This Rouse CR model was further examined for an orientation function S(n,t) = (1/a2)[u(x)(n,t)u(y)(n,t)] that describes fundamental features of viscoelastic relaxation. For CR relaxation, S(n,t) can be generally expanded with respect to the dielectrically determined functions, [f(p)(n)]2. Storage moduli, G’ and G-degrees’, were thus calculated at low omega from the experimental f(p) and model f(p)degrees, respectively. Corresponding to the difference between f(p) and f(p)degrees, G’ was not extremely but certainly larger than G-degrees’ at intermediate to high omega. This result was in harmony with viscoelastic data for long and dilute probe chains entangled with much shorter matrices, meaning that the dielectric and viscoelastic relaxation processes of such probe chains are consistently described by a non-Rouse type CR mechanism. Differences between the actual CR behavior and the prediction of the Rouse CR model were discussed in relation to extra relaxation at the chain ends that was not considered in the model.