With scanning electron microscopy, atomic force microscopy and polarizing optical microscopy, we have investigated the correlation of the alignment properties of a nematic liquid crystal (LC) 4-pentyl-4'-cyanobiphenyl with the thickness of LC films on holographic gratings. The spatial period and the height of the embossed ridges of the gratings are about 0.7 and 0.2 mu m, respectively. Our results indicate that the LC alignment properties depend on the thickness, d, of the LC film on the gratings: (1) uniform LC alignments are achieved when 10 < d < 30 mu m; (2) partially uniform LC alignments are recorded when 1 < d < 10 mu m; and (3) non-uniform LC alignments are resulted when d < 1 mu m or d > 30 mu m. The liquid crystalline film thickness dependent alignment properties can be explained in terms of the evolution of order-parameter as a function of the thickness of LC films. (c) 2006 Elsevier B.V. All rights reserved.