The evolution of research on the biochemistry of virus multiplication cannot be understood without knowing something of the structure of biochemistry and of virology before, during and immediately after World War II. My own research on virus multiplication began after studies on plant viruses and wartime research on the rickettsial components of the typhus vaccine, all of which involved work on the nucleic acids. Interest in the chemotherapy of virus disease led to a search for a model system. A simple (...) methodology for handling phage systems enabled biochemists to examine infected cells. The fortuitous use of an extremely virulent phage group (the T‐even phages) which evoke marked changes in polymeric products without affecting the production of energy and small building blocks facilitated these studies. An exaggerated synthesis of viral DNA by these phages concentrated our attention on the origins of this substance, which proved to contain a new pyrimidine deoxyribonucleotide, synthesized by a novel virus‐determined enzyme. The generality of the existence of virus‐induced enzymes and other proteins may be the key to a chemotherapy of virus infection. (shrink)