Three cases of phytanic acid storage disease with symptoms during the first months of life are reported. Hepatomegaly, facial dysmorphia, growth and/or mental retardation and osteopenia were observed in addition to retinitis pigmentosa and neurosensory deafness. The presence of phytanic acid in serum (160-320 mumol/1 (50-100 micrograms/ml)) was accompanied by hypocholesterolaemia. Electron microscopy showed that a storage material had accumulated in mesenchymal and parenchymal liver cells. Lamellar structures were seen in hepatocytes and other storing cells. These inclusions resembled the structures found in plant chloroplasts containing phytol. Some of the clinical and biological data obtained were consistent with Refsum's disease. However, other characteristics such as mental retardation, hepatomegaly, osteopenia, hypocholesterolaemia and hypoalphalipoproteinaemia, as well as the ultrastructural findings in the liver, suggested that our patients' illness was either a phytanic acid storage disease different from the classical form of Refsum's disease, or a more severe early symptomatic form of Refsum's disease. Early diagnosis by phytanic acid assay and electron microscopic liver examination calls for prescription of a low phytanate diet in the hope of improving the child's condition.