We report the case of a 49-year-old woman suffering combined central and peripheral demyelination, with serial magnetic resonance images scans illustrating the development of central demyelination in a patient with established chronic inflammatory demyelinating polyneuropathy. This is the sixth patient with this rare overlap syndrome reported to date. We review the available literature and argue that an inherited predisposition to both diseases is the most likely explanation for its occurrence. Copyright 1999 Harcourt Publishers Ltd.