The propositus was a 43-year-old Japanese male with a plasma total cholesterol (chol) level of 252 mg/dl and a high density lipoprotein (HDL)-chol of 169 mg/dl. His brother also had a markedly higher HDL-chol level of 149 mg/dl. In addition, his mother, sister and all 3 children had higher HDL-chol levels of 75-91 mg/dl. These data suggest that the propositus and his brother were homozygous for familial hyperalphalipoproteinemia (FHALP), whereas his mother, sister and 3 children were heterozygous for FHALP. None had any clinical signs of atherosclerosis. The propositus and his brother (homozygous FHALP) also showed markedly higher levels of apo AI (greater than or equal to 190 mg/dl) and E (greater than 16 mg/dl). Ultracentrifugal analysis disclosed an increase of HDL2-chol in the propositus. Cholesteryl ester transfer activity (CETA) was completely absent in the propositus (0.0% transfer/5 microliters/18 hr) and his brother (0.3% transfer/5 microliters/18 hr). It is concluded that this case is a family of homozygous FHALP probably caused by complete deficiency of CETA.