The mechanism of formation of tubular polythene film is a complicated process, and extensive studies have shown that the properties of the film made are influenced profoundly and in a complex way both by the processing conditions used by certain design features of the equipment. Studies of the effect of the extrusion variables on the more important film properties, both optical and mechanical, are reviewed in this paper. The results are discussed in terms of the fundamental nature of polythene film, its surface, its crystalline structure and its orientation.