The influence of visible light on the wave velocities in the [Ru(bpy)(3)](2+)-catalyzed Belousov-Zhabotinsky (BZ) reaction was investigated. The velocity was measured in a wide range of light intensities (0.047-7.24 mW/cm(2)) and concentrations of catalyst, sulfuric acid, and bromate. Light was found to decrease the velocity and even to inhibit the wave propagation completely. The velocity was also measured at different values of the thickness (0.20-1.39 mm) of the solution layer under illumination and the change was more pronounced in thin layers compared to thick ones. The inhibitory effect of light on the ruthenium-catalyzed BZ reaction is associated with additional bromide production in accordance with the photochemical properties of the ruthenium complex.