The invention relates to the use of a sulphated ion exchanger to selectively remove lipoproteins from blood plasma or serum. Although the attraction between sulphate groups and proteins has long been recognized it has now unexpectedly been found that cationic ion exchangers whose ion exchange capacity is provided by sulphate groups bind lipoproteins selectively in presence of other plasma or serum proteins and ions when they are equilibrated with solutions containing divalent cations and the same cation is added to the plasma or serum. Types of ion exchanger matrices and applications of the utlity are discussed.