A proposal is made to organize a meeting on genetic variation of viuses. The objective of this meeting is to bring together investigators in various disciplines to discuss the following: 1. Analysis of several groups of viruses by restriction enzymes, oligonucleotide fingerprinting, nucleic acid hybridization, and DNA and RNA sequencing procedures have demostrated that viruses within these groups vary considerably in nature. The objective of the meeting shall be to determine whether all or most virus species vary, and the extent of this variation. 2. In some instances, the variation in molecular structure has been used to trace the path of infection in animals and in humans. The full application of these techniques to the elucidation of the geographical habitat, ecology and epidemiology of viruses remains to be established. 3. Based on genetic variability, it is now feasible to identify the genes responsible for specific pathogenic manifestations of viruses in human hosts and to modify them for potential use in human prophylaxis. The conference will therefore cover 5 broad topics, i.e., (1) the structural and functional organization of viral genomes, (2) the extent of genetic variation presently known, (3) application and implications of detectable variation to problems in human health, (4) construction of altered genomes and (5) implications of genetic variation for evolution of viruses and genes.