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me to be here today to discuss the DNA provirus and RNA-directed DNA synthesis, and it has been a pleasure for my family and me to be here in Stockholm this week. The Nobel Prize is an honor not only for me but also for all those who have been working with avian RNA tumor viruses. The Nobel Prize is also an honor for the American people, whose tax dollars and private contributions have supported my work. The genetic information in RNA is transferred to DNA during the repli-cation of some viruses, including some that cause cancer. This transfer of information from the messenger molecule, RNA, to the genome molecule, DNA, apparently contradicted the “central dogma of molecular biology”, for-mulated in the late 1950’s. This mode of information transfer was first postu-lated and established for the replication of Rous sarcoma virus, a strongly transforming avian C-type ribodeoxyvirus. (Ribodeoxyviruses are RNA vi-ruses that replicate through a DNA intermediate.) In this lecture, I shall discuss the experiments that led to the formulation o