F-doped ZnO thin films were prepared by using the spray pyrolysis technique. The dependence of the electrical, optical, structural and morphological properties on the substrate temperature and spray solution acidity was studied. Additionally, aging of the spray solution presents a clear effect on the resistivity of ZnO thin films. The best films obtained show a resistivity, mobility and carrier concentration of the order of 1.5 x 10(-2) Ohm cm, 6 cm(2)/V s and 2 x 10(19) cm(-3), respectively. Wurtzite hexagonal structure, with a preferential growth along the [002] direction for all substrate temperatures and acidities used, was obtained, From scanning electron microscopy and atomic force microscopy analysis, it was determined that the grain size of the films decreases and its homogeneity increases when the acidity of the starting solution is increased. High optical transmittances, in the order of 90%, were obtained in all the cases. (C) 2002 Elsevier Science B.V. All rights reserved.