The susceptibility of brown trout (Salmo trutta) to two strains of infectious hematopoietic necrosis virus (IHNV) is reported. Waterborne exposures to virus were done on 25 fish groups at four concentrations (10 - 10 )of a type-1 strain of IHNV obtained from Oregon, USA and a type-2 strain of IHNV obtained from Idaho, USA. Brown trout had a cumulative percent mortality which ranged from 48-12% when infected with the type-1 strain and 36-12% for the type-2 strain. Mean number of days to death tended to increase with decreased virus concentration used in the waterborne exposure for both strains. There were no major differences in the mean number of days to death for fish infected with type-1 strain at a given concentration when compared to the type-2 strain. Although brown trout were susceptible to both strains of IHNV this species appears to be more refractory to infection than rainbow trout (Oncorhynchus mykiss).