The present invention relates to new and improved interleukin-7 polypeptides, as well as compositions comprising the same, their preparation and uses. The invention more particularly relates to hyperglycosylated IL-7 polypeptides having improved properties, as well as their manufacture and therapeutic uses. The invention also discloses novel IL-7 polypeptides having modified amino acid sequences containing artificially created glycosylation site(s), as well as corresponding nucleic acid molecules, vectors and recombinant host cells. The invention also relates to the use of such polypeptides, cells or nucleic acids for curative or preventive treatment of mammalian subjects, including human subjects.