Three patients with heterozygote type IIa hyperlipoproteinemia were treated by specific LDL apheresis with a dextran sulfate-cellulose column every two weeks. Each apheresis resulted in a fall in total cholesterolemia of about 50 p. 100 with a parallel fall in apoprotein B. The average drop of 15 p. 100 in HDL-cholesterol appeared to be due to the hemodilution induced at the end of apheresis. After two months, cholesterol and apoprotein B concentrations before removal were 15 p. 100 lower than baseline values. Treatment was well tolerated. These findings appear encouraging for the treatment of heterozygote forms of familial hyperlipoproteinemia resistant to chemotherapy.