Thirteen members of a kindred were studied who had hypobetalipoproteinemia and presented with signs and symptoms of a spinocerebellar degeneration similar to Friiedreich's ataxia. Findings in the 20-year-old proband included: (1) low fasting cholesterol and beta lipoprotein levels; (2) low to normal serum and red cell tocopherol levels; (3) slow sensory (mixed antidromic) nerve conductiion velocities in tibial, peroneal, and median nerves, with normal motor conduction velocities; (4) normal fat absorption and jejunal biopsy; and (5) absence of acanthocytosis. Further, the serum very low density, low density, and high density lipoproteins and their apopro-teins showed no major differences from normal. Four of the family had low to normal serum cholesterol levels; neurologic signs were observed only in an 11-year-old brother and in a seven-year-old sister.