Thin films of V1-xMoxO2 (x=0-0.041) for thermochromic windows were formed by dual-target reactive magnetron sputtering. The composition, crystal structure, morphology and optical properties of the films were evaluated by Rutherford backscattering spectrometry (RBS), X-ray diffraction (XRD), atomic force microscopy (AFM) and spectrophotometry respectively. The relationship between the transition temperature tau(c) and x in V1-xMoxO2 was clarified through precise determinations of the dopant concentration and the value of tau(c). A linear reduction in tau(c) by approximately -12 degrees C (at.% Mo)(-1) was confirmed for the films with least doping, while the reduction efficiency decreased with higher dopant concentrations. V1-xMoxO2 films with desired x values were also fabricated using a V-Mo (Mo, 4.0 at.%)alloy target. Investigations of the thermochromism of the V1-xMoxO2 films suggest their potential for advanced windows.