The results from steady-state extrusion studies with commercially pure aluminum using the visioplasticity method for analysis showed that interfacial friction between billet and tool influences the velocity distribution in the entire plastic zone. It was found that for well-lubricated billets, the tool-billet interface tends toward a stream line. It was found further that a reversal in sign of the resolved shear stresses and the coefficients of friction occurs in the interfacial material in the conical section of the die. An explanation for this anomaly has not yet been found, but it is believed that this behavior is due to the mechanism of plastic flow within the billet.