In this work, the statistical characteristics of the surface of a water film, freely falling down a vertical or inclined flat plate, have been investigated. The study was carried out in the frame of a research on passive cooling of heated surfaces by the evaporation of thin water films. The experiments, performed to confirm and extend previous results by the same authors, involved relatively cold water (ambient temperature or slightly warmer 20-30 degreesC) and warm water (50 and 70 degreesC). The range of Reynolds numbers includes the classical threshold for the transition between the laminar-wavy and the turbulent regimes. Two different plate inclinations with respect to the vertical position have been addressed (0degrees and 45degrees). Capacitance probes were adopted to collect discrete film thickness time series, which have been processed to extract relevant statistical data. A specific probe configuration including an electrical heating system has been developed in order to overcome the problem of vapour condensation onto the active surfaces of the electrodes in the presence of warm water. Data on mean, minimum and maximum film thickness as well as standard deviation and wave velocity are presented, discussing the trends observed as a function of film flow rate, plate inclination and film temperature, also considering the information coming from previous experimental campaigns. (C) 2002 Elsevier Science Ltd. All rights reserved.