In this paper, we show that under appropriate deposition conditions, epitaxial films of La2/3Ca1/3MnO3 can grow fully strained on SrTiO3 (STO) single-crystalline substrates up to thicknesses as large as 180 nm. In particular, the growth rate appears to be a critical parameter. The microstructure of fully strained films of different thickness values is analyzed by high-resolution transmission electron microscopy, showing sharp interfaces and no misfit dislocations, The magnetotransport properties axe studied as a function of thickness, It is found that, despite the absence of steric effects related to strain relaxation, the metal-to-insulator transition temperature is reduced from 270 K for the 180 nm films to some 100 K for the thinner films thus revealing the increasing influence of the interface of the film with the substrate. (C) 2002 Elsevier Science B.V. All rights reserved.