The preparation of highly crystalline polyethylene at low pressure is reported. We demonstrate that with careful control of the substrate, melting and crystallization schedule, and physical state of the specimen (film thickness), it is possible to prepare polyethylene having a density in excess of 0.999 g cm−3, a melting temperature of ∼140°C, and a heat of fusion in excess of 70 cal/g. The approach appears to be general and should be applicable to a wide variety of polymers. An analysis of the heat‐of‐fusion data suggests a value of 79 cal g−1for the infinitely extended chain crystal.