Epitaxial growth produces oriented crystal projections where a long unit cell axis is parallel to the major crystal face rather than perpendicular to it and thus provides a favorable condition for electron diffraction data collection which minimizes perturbations due to elastic crystal bending. Even though the crystals are not so perfect as those produced by solution growth, the intensity data from them have been useful for the quantitative crystal structure analysis of several molecular organic compounds and linear polymers as discussed in this review.