Several anomalies are observed in the flow of the melts of many elastomers which are not commonly observed with melts of plastics. A stress-oscillation at high rates of shear and a tendency to reach a constant level of stress at lower rates of shear are two of the more commonly encountered anomalies. Both anomalies occasionally occur in the flow of a single melt. The role of molecular weight, molecular weight distribution and branching in producing anomalous flow is demonstrated. The presence of supermolecular flow units is invoked to explain certain anomalies and supporting evidence is presented. The data strongly suggest changes in the rheological flow units take place as the conditions of shear are changed. The flow properties of many elastomers are complicated by the severe mechanical degradation taking place under these conditions of shear. Anomalous flow patterns can be either produced or removed by mechanical degradation depending upon the specific elastomer system. The extent of degradation appears to be dependent upon the flow unit governing the flow process and independent of the shearing stress or work input per unit volume of polymer sheared. The complexity and distribution of entanglements play a major role in the flow processes as well as in the mechanical degradation process of certain elastomers.