We report a case of Baló's concentric sclerosis (a variant of multiple sclerosis) from Papua New Guinea. A 42-year-old woman with a past episode of optic neuritis presented with a left hemiparesis. Magnetic resonance imaging revealed a solitary large tumour-like right cerebral lesion with a pattern of concentric bands of different signal intensities. The diagnosis was established by biopsy of the lesion. To our knowledge, this is the first reported case of Baló's concentric sclerosis in the indigenous population of Papua New Guinea. Copyright 1999 Harcourt Publishers Ltd.