Zr1-xAlxN thin films, with 0 <= x <= 0.73, have been synthesized by magnetron sputtering. The phases and the electrical and optical properties have been investigated. For x <= 0.43, the Zr1-xAlxN films crystallize in cubic NaCl type of structure (B1 type), while at higher Al content, 0.43 < x <= 0.73, the films contain two phases: the cubic ZrN and the hexagonal AlN phases poorly crystallize. Here, we report on the physical properties of the ternary single-phase Zr1-xAlxN compounds as a function of x over the range 0 <= x <= 0.43. The optical and the electrical properties of the B1-Zr1-xAlxN films depend on x. The effective density N* of conduction electrons and the free charge carrier scattering time tau decrease monotonously as the Al content increases, whereas the room-temperature dc resistivity measured by the van der Pauw method increases from 260 to 2260 mu Omega cm for x=0.43. The observed trends are correlated with changes in the electronic structure due to the substitution of Zr by Al atoms. The optical properties are well described by a Drude-Lorentz model, while a straightforward model of phonon-alloy scattering and grain boundary scattering account for the electronic transport properties. (c) 2004 Elsevier B.V. All rights reserved.