Crystallization of a polymer while it is subjected to orientation has recently become a subject of great interest. This introductory study is concerned with inducing crystallization under the influence of pressure and orientation and also with the nature of the crystalline structure so formed from two commercial high density polyethylenes. The resins utilized are Phillips Marlex 6009 having a melt index of 0,9 and Dupont Alathon 7050 having a melt index of 2.1. As most of the experiments were conducted on the Dupont samples, the subject will be Alathon 7050 unless noted otherwise. The Marlex 6009, with its distinctly different melt index, was largely used to confirm the generality of the phenomena observed with the Alathon 7050. Crystallization is induced in a capillary of 0.0508 cm. diameter, 2.56 cm. length, and 90° entrance angle by means of an Instron Capillary Rheometer operating at constant plunger velocity.