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 H2N 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=—NH2, —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.