We designed experiments to ascertain whether area V5 of human visual cortex is activated by a motion stimulus in which luminance is made irrelevant, and motion is generated from hue differences alone. The stimuli consisted of moving green squares or bars against a red background, masked with luminance noise. Changes in regional cerebral blood flow (rCBF) were determined by the technique of positron emission tomography and the brain images thus derived were co-registered with magnetic resonance images of the same brain to identify the anatomical locations of the blood flow changes. The results showed that when subjects perceived motion, a change in rCBF occurs in areas V5, V1/2, V3 and the parieto-occipital sulcus but not V4, even though the moving stimulus was defined by hue. We conclude that the motion-specialized areas of the visual cortex can use information derived from any source to undertake their function.