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The neurotoxicity of lead to the adult brain is less well-known than that seen in children. It may present as acute severe encephalopathy or as chronic cognitive and behavioural symptoms, either in isolation or with systemic features of lead intoxication. Magnetic resonance imaging findings in lead encephalopathy vary. The pathogenesis of lead encephalopathy and its effects on cognition both during development and in the adult are discussed. That encephalopathic symptoms do not correlate with blood lead levels and that they may persist after chelation are highlighted. As an illustration, we describe a patient with chronic cumulative lead intoxication, who presented with peripheral neuropathy, anaemia, and a 'lead line' on the gingiva. She had cognitive dysfunction with extensive subcortical and cerebellar white matter lesions on magnetic resonance imaging. An area of restricted diffusion in both frontal regions is likely to be due to active ongoing demyelinating at the 'leading edge' of the lesion. Although systemic features and the peripheral neuropathy improved with chelation, the encephalopathy showed only marginal change, with later appearance of a symmetric akinetic-rigid state.