The research of host-virus relations enriched the world of science with invaluable scientific and practical results in the past half of this century.In the last several years the interest in virus hosts and non-hosts has a real renaissance.Hosts and non-hosts play an important role in throwing light upon virus epidemiological problems and correlations.Furthermore,the artificial hosts are indispensable i virus identification,separation and preservation.The non-hosts virus resistance and in virus separation.The breeding research for virus resistance is aimed all over the world at spotting the resistance genes of wild plant species and using this knowledge in practice; the basis of this work is also formed by the investigations into the virus host ranges. This widely extended scientific work is equally important both from the theoretical and practical points of view.