X‐ray‐diffraction measurements were performed on smectic A octylcyanobiphenyl liquid‐crystal (LC) films deposited on glass and silicon gratings with periods between 664 nm and 200 &mgr;m. The film’s two interfaces, air‐LC and LC‐grating, imposed boundary conditions that required different alignments for the minimum energy configuration; the competition between these two forces was studied in thick (30+ &mgr;m) films. Consistent with earlier work, gratings with periods on the order of 10 &mgr;m and depths of 1.5–3 &mgr;m induced a portion of the film into homogeneous alignment in the direction of the grooves. As expected from theory, longer‐period 200 &mgr;m gratings with the same depth showed an inconsistent ability to produce an inplane alignment; however, contrary to theory, shallower 664 nm gratings also failed to consistently induce in‐plane alignment and did not produce an azimuthal preference. The results from the x‐ray scans were fit with a multilayer model to give estimates of the thicknesses, orientations, and mosaic spreads of the different regions in the films. Films having an in‐plane component were estimated to have a 5–10‐&mgr;m‐thick homeotropic skin at the surface. On 9 and 15 &mgr;m gratings, the in‐plane scattering arose from a single homogeneous region in which the molecules had a small tilt (up to 5°) with respect to the plane of the substrate. The director was not exactly parallel to the grooves but was offset by up to 20°, and the mosaic spread in the azimuthal direction was typically 20°. In some films there was an additional region that appeared to be disordered. ©1995 American Institute of Physics.