[Oncornaviruses and human leukemias]

This is a brief review on current progresses which appeared recently on the isolation of a putative human oncornavirus from human leukemic cells. There are strong arguments in favor of the existence of such an oncornavirus, both indirect (existence of viral nucleotide sequences and viral proteins in human leukemic cells), and direct (isolation of a Type-C virus from in vitro cultures of human leukemic cells).