Conjugates of transferrin, albumin and polyethylence glycol consisting of native or thiolated transferrin or albumin or of polyethylene glycol (MW between approximately 5,000 and 20,0000) with at least one HS--, HO-- or H.sub.2 N group and cytostatic compounds derived through maleinimide or N-hydroxysuccinimide ester compounds, such as doxorubicin, daunorubicin, epirubicin, idarubicin, mitoxandrone, chloroambucil, melphalan, 5-fluorouracyl, 5'-desoxy-5-fluorouridine, thioguanine, methotrexate, paclitaxel, docetaxel, topotecan, 9-aminocamptothecin, etoposide, teniposide, mitopodoside, vinblastine, vincristine, vindesine, vinorelbine or a compound of general formula A, B, C or D, where n=0-6, X=--NH.sub.2, --OH, --COOH, --O--CO--R--COR*, --NH--CO--R--COR*, where R is an aliphatic carbon chain with 1-6 carbon atoms or a substituted or unsubstituted phenylene group and R* H, phenyl, alkyl with 1-6 carbon atoms.