Sexithiophene (6T) films have been grown by molecular beam deposition on two different substrates: a clean Cu(110) single crystal surface and a 1:1 Cu(110)/Cu(110)-(2 x 1)O stripe surface. Both substrates serve as atomically ordered two-fold symmetric templates, which induce epitaxial growth of the 6T crystallites due to surface corrugations. On both surfaces, 6T crystallizes in its low-temperature phase with (010) being the main crystallographic orientation of the 6T crystals relative to the substrate surface. Two different epitaxial growth behaviors are observed: while on the oxygen-passivated surface the long molecular axes of the 6T molecules are aligned exactly along the oxygen rows, small tilt angles relative to the densely packed copper rows are found on the clean copper surface. Classical misfit calculations seem to be insufficient to describe the observed epitaxial crystallization of sexithiophene. On the striped surface clean copper- and oxygen-passivated copper regions are offered on the same surface. The dominant crystalline fraction grows in an orientation also found on the fully reconstructed Cu(110)-(2 x 1)O surface where it grows exclusively in this orientation. A model that explains these experimental findings is discussed and it turns out that the sticking anisotropy is the dominating effect. (C) 2009 Elsevier B.V. All rights reserved.