Tracer diffusion coefficient, D*, and the Newtonian zero shear-rate viscosity, eta(0), were measured for a high molecular weight random copolymer (SAN) of styrene and acrylonitrile. As predicted by the reptation model, D* was in agreement with the molecular-weight sealing of M(W)(-2) (M(W) is the weight average molecular weight of the chain being probed) and was independent of matrix molecular weight; eta(0) showed a molecular-weight scaling of M(W)(3/4). While the temperature dependence of these two relaxation processes could be well explained by the free-volume model up to 252 degrees C, they showed a discrepancy in activation enthalpy, E(a), of about 20%, with a larger value for diffusion.