Abstract: A material inspection system, such as a baggage insepction system, uses x-ray imaging to identify organic materials such as drugs and explosives. The articles being inspected are transirradiated with x-rays having different radiation energies. From detected radiation, attenuated by the article under inspection, a materials information signal and a luminance signal are formed. The color of the monitor image is controlled by the materials information signal, and the image brightness, color saturation and white content of the image are controlled by the luminance signal. A color portrayal occurs only when the materials information signal has a sufficiently high signal-to-noise ratio.