Abstract The influence of the stretching of a dense form of trans (CH)x on its morphology and its crystallographic structure is examined. It appears that a mosaic as low as ± 5° can be obtained for elongation ratios higher than 10. The coherence lengths measured along and perpendicularly to the polymer chain axis are respectively equal to 150 and 100 Å. An average Pnam orthorhombical structure is proposed based on the analysis of a large number of X-ray diffraction reflections. Our results are compared with others previously published in the literature and related to polymers synthesized with different methods.