Abstract: The present invention relates to liposomes for drug delivery, wherein a liposome includes molecules of at least one desired drug distributed within an aqueous phase in the interior of the liposome and wherein the liposome further includes molecules of the same or of another drug attached to either or both sides of the liposomal membrane. More specifically, the invention relates to liposomes, wherein at least a part of the molecules of a desired drug bear a functional group that is reactive with a functional group present in at least one lipid fraction, and wherein the drug is covalently linked to the membrane lipids by chemical bonding, e.g. by ester bonding of a hydroxyl group of a lipid molecule and an acidic residue of the drug. In a preferred embodiment, the desired drug is a glycoprotein such as erythropoietin. The invention further relates to a method of manufacture of said liposomes and to pharmaceutical compositions containing them.