We have used the technique of functional magnetic resonance imaging (fMRI) and a variety of colour paradigms to activate the human brain regions selective for colour. We show here that the region defined previously [Lueck et al. (1989) Nature, 340, 386-389; Zeki et al. (1991) J. Neurosci., 11, 641-649; McKeefry & Zeki (1997) Brain, 120, 2229-2242] as the human colour centre consists of two subdivisions, a posterior one, which we call V4 and an anterior one, which we refer to as V4alpha, the two together being part of the V4-complex. The posterior area is retinotopically organized while the anterior is not. We discuss our new findings in the context of previous studies of the cortical colour processing system in humans and monkeys. Our new insight into the organization of the colour centre in the human brain may also account for the variability in both severity and degree of recovery from lesions producing cerebral colour blindness (achromatopsia).