The growth behaviour and crystalline quality of c axis oriented PbTiO3 thin films deposited on 5.5 degrees vicinal MgO(100) substrates by r.f. magnetron sputtering have been studied in comparison with those on exact MgO(100) substrates. The film on the vicinal substrate grew epitaxially along a crystallographic direction but slight misorientation occurred owing to the presence of vertical lattice mismatch between the film and the steps on the substrate surface. Detailed X-ray diffraction studies revealed that the film of a cubic phase above the Curie temperature was misoriented by 0.7 degrees with respect to the [100] direction of the substrate, while c and a domains of a tetragonal phase at room temperature were misoriented by 1 degrees and 0.5 degrees respectively. The crystalline quality of the film on the vicinal substrate was also found to be superior to that on the exact substrate.