Six species belonging to two genera of Cicadellidae and six species in four genera of Delphacidae transmit viruses and MLO of rice in Asia. Vector specificity was found to characterize the biological relationship between plant viruses and their vector species. From the standpoint of the ecology and epidemiology of virus diseases, it is suggested that the concept of specificity should be broadened and include biological and ecological characters of vector species such as geographical distribution, seasonal prevalence, migration, dispersion and behavior as well as transmission efficiency. Most rice virus diseases, especially leafhopper-borne diseases, are found in some restricted areas within the distribution of vector species. The epidemics of green rice leafhopper-borne virus diseases of rice in Asia - such as tungro in the tropics, transitory yellowing in the subtropics, and dwarf in the temperate region - are closely associated with the predominance and seasonal prevalence of highly efficient vector species.