We report the epitaxial polymerization and characterization of poly(p-oxybenzoate) (POBA) on various crystalline substrates. Acetoxybenzoic acid was polymerized onto solid crystalline substrates immersed in the paraffin solution. The resulting POBA films were characterized by polarized Fourier transform infra-red spectroscopy, transmission electron microscopy, scanning electron microscopy, wide-angle X-ray diffraction, and electron diffraction. The morphology of the POBA films was found to depend on the polymerization conditions and crystal structures of substrate. On single-crystal mica and KBr substrates, POBA films formed layer-like structures with their crystal c-axes (chain axis) parallel to the substrate surface with azimuthal orientations. On polycrystalline gold, the POBA him consisted of lamellae standing with the c-axis parallel to the gold surface. For all of the above substrates, a small disturbance (light shaking of the reaction flask) at the beginning of the reaction results in POBA lamellar morphology with the c-axis vertical to the surface, showing that early-stage nucleation determines morphology and orientation of the POBA crystal growth.