Moiré lines of bilayered polyethylene single crystals, superposed with slightly different orientation, changed their spacing and orientation locally in limited regions of several thousand angstroms when annealed at temperatures higher than their crystallization temperature. A pair of terminating moiré half-lines with opposite signs were found around these regions. The edge dislocation density was measured at various annealing temperatures as a function of time. On the basis of the results, a mechanism of generation of the edge dislocations is presented. During annealing, lattice planes in the limited regions of the bilayered crystals are sheared in a direction that reduces the orientational mismatch angle. In the domain of the sheared region the two lamellae come in close contact to form a network of screw dislocations between them. Edge dislocations are generated at the boundary of the sheared region. The size of the sheared region can be evaluated thermodynamically provided that the free energy of formation of the sheared region is minimized. Observed sizes of the sheared regions were found to be comparable with the calculated values. The fact that the images of the moiré lines of the as-grown crystals, kept for a prolonged time at the crystallization temperature in their mother liquor, were frequently changed into those of the screw dislocations or the moiré lines similar to those found in the annealed crystals is interpreted by the same theoretical considerations.