The feasibility of using low density lipoprotein(LDL) as a selective drug-targeting vehicle is examined in this thesis. A number of animal tumours are seen to express considerable receptor-mediated uptake of the lipoprotein. The organs likely to suffer during chemotherapy using this carrier, viz. liver and adrenals, are afforded some protection by the administration of bile salts and hydrocortisone respectively. Several methods are employed for incorporating adriamycin, chlorambucil and daunomycin into LDL and the drug-LDL complexes so formed show enhanced cytotoxicity in vitro and in vivo. It is likely that LDL will be a useful targeting vehicle for anticancer agents if the level of drug incorporation can be increased.