Lipid chemical analysis of a case of membranous lipodystrophy (Nasu-Hakola disease) was reported. The case is a 43 yr-old man (at death). Onset of the disease was at his age of 10 when he had complained of leg pain. Since his age of 14, he had bone fractures of the lower extremities many times. At the age of 35, he was admitted to a hospital for the neurological examination. At that time, he showed exaggerated tendon reflexes and intension tremor of the upper extremities. He was euphoric and demented. His IQ was 31. Histological examination of biopsy specimen from the bone marrow revealed the typical membrano-cystic lesion. He had status epilepticus which was followed by comatous state for a week. The disease progressed gradually and he fell into decorticated state. He died at the age of 43. The total clinical course was 33 years. The brain weighed 680 g. Remarkable atrophy was observed in the whole brain. Loss of nerve cells in the upper layers of the cortex was marked. There were loss of myelin sheath and severe gliosis in the white matter. A part of the brain, liver and subcutaneous fat was frozen at the time of autopsy for the chemical examination. Quantitative determination of cholesterol, glycolipid, phospholipid, free fatty acid in the brain and liver, cholesterol, free fatty acid, triglyceride in the subcutaneous fat were carried out. Cholesterol was decreased about 33% in the cortex and 42% in the white matter in comparing with those of controls and the content of cerbroside in the white matter was about 1/3 of that of controls.(ABSTRACT TRUNCATED AT 250 WORDS)