Peripheral nerve morphometry was assessed in four patients with Tangier disease. Three patients with a relapsing and remitting multiple mononeuropathy had prominent peripheral nerve demyelination and remyelination with affected internodes clustered along particular nerve fibres. Putative lipid vacuoles were almost exclusively confined in this multifocal neuropathy syndrome to Remak cells. By contrast a fourth patient with a slowly progressive syringomyelia-like neuropathy had advanced peripheral nerve degeneration and a more global distribution of lipid vacuoles within peripheral nerve. A review of Tangier disease in the literature indicated the possibility of additional peripheral nerve syndromes. The clinical heterogeneity raises the possibility of different metabolic errors in Tangier disease or a common metabolic error subject to genetic influences. The results of this study indicate that normal serum cholesterol levels do not exclude a diagnosis of Tangier disease. It is therefore advisable to determine both high density lipoproteins and serum cholesterol levels in patients with undiagnosed multifocal neuropathy or syringomyelia-like syndromes.