The onset of extrudate distortion (sharkskin) in linear low‐density polyethylene is shown to coincide with the failure of adhesion at the polymer/metal interface. The transition to slip‐stick melt fracture is characterized by a catastrophic failure of adhesion, with periodic nearly complete slip over a capillary residence time alternating with adhesion. The onset of sharkskin is in agreement with a calculation based on a stability theory of Pearson and Petrie.