A 43-year-old male with a high value of high density lipoprotein cholesterol (151 mg/dl) was found among subjects receiving annual health checks. We investigated the cholesteryl ester transfer protein (CETP) activity and conducted a family study. There was complete deficiency of CETP activities in the proband and his sister, and partial deficiency of CETP activities in his mother and daughter. Genetic analysis revealed a splicing defect (G to A point mutation) in intron 14 of the CETP gene.