50/50 wt % blends of isotactic polypropene (i-PP) with metallocene-based random poly(ethene-co-1-butene) (PEB) were prepared with 1-butene content varied from 52 to 100 wt %. The melt miscibility of the i-PP/PEB blends as a function of 1 -butene content was studied by investigating the morphologies of the blends in the solid state by phase-imaging tapping mode atomic force microscopy (AFM) and transmission electron microscopy(TEM). It was found that i-PP is melt miscible with FEB for 1-butene contents of approximate to 88 wt % (miscibility window). Differential scanning calorimetry (DSC) analysis showed a slower and hindered i-PP crystallization in the miscible or partially miscible blends. Intensive investigations on the apparently one-phase blend were performed by optical microscopy, small-angle X-ray scattering and dynamic mechanical analysis.