A control system for improving the homogeneity of transparent conductive oxide films deposited by reactive magnetron sputtering has been set up for large area in-line coating. The control system monitors operating points along the target axis by measuring the reactive gas partial pressure and a closed loop control of power and gas inlet maintains a user-defined partial pressure distribution. A deviation from set points and switching of local target states into metallic or oxide mode is prevented. As a result, the film properties such as sheet resistance, optical performance and film thickness show an improved homogeneity along the target axis. (c) 2005 Elsevier B.V. All rights reserved.