The knowledge on the binding of vanadium ions and complexes to serum proteins and how vanadium might be transported in blood and up-taken by cells has received much attention during the last decade, particularly as far as the transport of VIVO2+ is concerned. In this work we revise and discuss some relevant aspects of previous research, namely the two main types of binding proposed for transport of VIVO(carrier)2 complexes. New results, obtained by circular dichroism (CD), EPR and gel electrophoresis, regarding the binding of vanadium to hTF in the oxidation states +5 and +3 are also presented. Namely, evidences for the binding of V V-species to diferric-transferrin, designated by (Fe III)2hTF, as well as to (AlIII)2hTF, are presented and discussed, the possibility of up-take of vanadate by cells through (FeIII)2hTF endocytosis being suggested. It is also confirmed that VIII binds strongly to hTF, forming di-vanadium(III)-transferrin, designated by (VIII)2hTF, and gel electrophoresis experiments indicate that (VIII) 2hTF corresponds to a 'closed conformation' similar to (Fe III)2hTF.