The influence of crystallization conditions on the morphology of the contact layer of high-density polyethylene crystallized on graphite has been investigated. The characteristic morphology of the polyethylene contact layer consists of striated, ribbonlike structures organized in domains in which the striations follow the same direction. The directions in different domains reflect the threefold symmetry of the graphite lattice. From the dependence of the width of ribbons on the crystallization conditions (i.e., the cooling rate and annealing), it has been concluded that the polymer chain is aligned parallel to the striation directions and that the ribbon width corresponds to the lamellar width. Therefore, the lamellar width in the contact layer (60 and 80 nm for cooling rates of 10 and 0.2degrees/min, respectively) is considerably bigger than in the bulk (ca. 26 nm). In addition, the chain orientation can be uniform over large areas, but the domain orientation can be disturbed by the presence of pits only one atomic layer deep (0.335 nm) if they are formed on the graphite surface. These results show the great importance of the nanostructure of the support for polymer chain alignment and epitaxial crystallization of polymers.