The results of virological examination of diseased herbivorous fishes and some biological properties of viruses isolated are given in this paper. Examination of fish was carried out in 1986 at farms suspected of the presence of spring viraemia of carp . Yearlings of silver carp (Hypophthalmichthys molitrix), bighead (Aristichthys nobilis), grass carp (Ctenopharyngodon idella) and farmed carp (Cyprinus carpio) were examined. At one of the farms, SVC virus was isolated from bighead and grass carp yearlings experiencing increased mortality during an outbreak of SVC in the common carp. The highest mortalities occurred when the water temperature was in the range 13-17 degrees C.The affected bighead and grass carp appeared weak and had necrotic dorsal and caudal fins and occasional haemorrhages in the eyes. Both species were su s ceptible to experimental infection by bath challenge and by co-habitation.