AbstractThe melt‐filled portion of an extruder screw has been examined in a quantitative analytical fashion by numerous workers during recent years. The progress which has been made in defining flow patterns in this portion of the screw is reviewed, with special attention devoted to edge effects of the screw flights and the contribution of the circulatory cross‐channel component of flow. More recent work on the complex problem introduced by the existence of curvature in the screw channel is presented, along with consideration of distortion of the streamlines caused by non‐isothermal conditions and non‐Newtonian fluid properties of the molten