The crystallization behavior of isotactic poly(1-butene) (iPBu) from melt on the surface of melt-drawn oriented isotactic polypropylene (iPP) thin films and in the melt-drawn oriented iPBu/ iPP blend thin films was studied. It has been found that iPBu in the melt-drawn iPBu/iPP blend films is form I crystals like in the melt-drawn thin films on its own. The form I iPBu crystals exhibit, however, an oriented edge-on lamellar structure rather than the fibrils or shish crystals observed in melt-drawn pure iPBu films, reflecting the influence of iPP on the melt-draw behavior of iPBu. Melt recrystallization of iPBu in the iPBu/iPP melt-drawn films does not change its orientation status and crystalline modification, reflecting the epitaxial capability of iPBu on oriented iPP. This has been further confirmed by oriented form I crystallization of the spin-coated iPBu thin films from melt on oriented iPP melt-drawn films, which eliminates the confinement effect on the form I iPBu crystallization in the melt-drawn iPBu/iPP film. In situ IR study also confirms that the high melting temperature form I iPBu crystals are directly formed on the iPP substrate. The IR results further demonstrated that the crystallization of form I iPBu at 104 degrees C on iPP substrate is faster than its form II. Taking all of the experimental results into account, the epitaxial crystallization of iPBu on oriented iPP substrate in its form I is believed to be the synergistic effect of lattice matching between iPP and form I iPBu as well as the crystallization kinetics of iPBu.