Two homozygous familial hypercholesterolemic patients were treated with dextran-sulfate cellulose LDL-apheresis (DSC-LDL/A). We evaluated qualitatively and quantitatively, red cell and platelets membrane cholesterol and fatty acids, before and after LDL-apheresis. Fatty acids and cholesterol of red blood cells and platelets were determined by gas-chromatographic technique. We failed to observe any quantitative or qualitative modification, as far as the youngest patient (MD) is concerned. Only in the oldest patient (SM), docosaesanoic acid (22:6) values, were significantly reduced by LDL-A on quantitative basis. In the same patient, also mirystic acid (14:0) values, were significantly decreased as determined by qualitative method. The above mentioned fatty acids were significantly changed in platelets on treatment with LDL-apheresis performed on weekly basis.