The surface morphology and dynamic scaling behavior of Al thin films sputter-deposited on rough Ti(l 0 0) substrates were studied by atomic force microscopy (AFM). It was found that the rough Ti(I 0 0) substrates played a crucial role in determining the surface morphology and roughness evolution of Al thin films at the initial stage of the film growth. Due to the substrate roughness contribution, a smoothing effect of initially rough surfaces could be observed. Also, surface roughness increased at a relatively low rate in the early growth time. The roughness exponent alpha and growth exponent beta for Al film is were determined to be 0.79 +/- 10.05 and 0.16 +/- 10.01, respectively. The observed substrate effect on the evolution of surface roughness was also discussed in terms of the competition between the substrate roughness contribution and the growth-induced roughening. (C) 2003 Elsevier B.V. All rights reserved.