Multiple melting behavior of poly(butylene-2,6-naphthalate) (PBN) was studied with X-ray analysis and differential scanning calorimetry (DSC). Double endothermic peaks L and H attributed to the cc-form crystal modification, a small peak attributed to the beta-form crystal modification, and a new shoulder peak S at a lower temperature of peak H appeared in the DSC melting curves. Wide-angle X-ray diffraction patterns of the samples isothermally crystallized at 200 and 220 degrees C were obtained at a heating rate of 1 K min(-1), successively. In this heating process, change of crystal structure and increase of quantity of the beta-form crystallites could not be observed up to the final melting. With increasing temperature, the diffraction intensity decreased gradually and then increased distinctly before a steep decrease due to the final melting. The X-ray analysis clearly proved the melt-recrystallization during heating. The beta-form crystal modification was formed during slow heating process in the high temperature region. (c) 2005 Elsevier Ltd. All rights reserved.