For decades retroviruses have been riding the crest of a wave of experimental research directed toward the identification of an infectious agent of human neoplastic diseases. In the early 1970s, several scientists successfully demonstrated the presence of retroviruses in numerous animal species and proved their etiological role in some related diseases. Corresponding findings in humans were somewhat discouraging. Although financial support for this line. of research declined, a few dedicated retrovirologists survived and continued to collect more biological information and technological...