The miscibility and morphology of poly(E-caprolactone) (PCl) and poly(para-chlorostyrene) (PpClS) blend were investigated by using thermal analysis, morphological analysis, viscometry, and the study of melting point depression. A single glass transition temperature was observed by differential scanning calorimetry (DSC) for PCl/PpClS blends in the whole compositional range (0/100, 25/75, 50150, 62.5/37.5, 75/25, 90/10). Morphology of the polymers and their blends was studied by scanning electron microscopy (SEM). The Fourier transform infrared spectra of the samples were obtained by spectrometer. Up to 12 cm(-1) shifts in carbonyl stretching band of PCl was detected in the spectra of PpClS rich blends. The viscosity of PCl, PpClS and their blends has also been studied to investigate the miscibility according the miscibility criteria Delta b, and Delta[eta]. Using this data, the interaction parameters alpha and mu, based on the Chee and Sun et al. approaches were determined. These criteria indicated that the blend is miscible in all proportions up to 90%) of PC] content in the blends. The melting point depression of PCl in the blends was examined to obtain the interaction parameter, chi(12) for this system. The parameter, chi(12) was found to be composition dependent. Negative values of the obtained interaction parameter also support the miscibility of this system up to the 90% PCl in the blend. (c) 2006 Elsevier Ltd. All rights reserved.