Adsorption of infectious hematopoietic necrosis virus (IHNV) to sea sand, Japanese acid clay, diatomaceous earth, kaolin, bentonite, quartz sand, chitin, cellulose powder, ion exchange hydrophobic Toyopeal and Cellulofine, alundum, active carbon, silica gel, glass, plastic, and bacterial cells was studied. The IHNV adsorbed to several clays (kaolin, bentonite, Japanese acid clay) and diatomaceous earth in sterilized water with a wide range of pH (5-11) at concentrations of 1, 10, and 100 mg/mL. Except for bentonite, infectivity of clay-adsorbed IHNV persisted for as long as 9 weeks. The clay-adsorbed IHNV also persisted in infectivity to rainbow trout Oncorhynchus mykiss, causing cumulative mortality rates of more than 73%. The results suggest that IHNV adsorbed to naturally occurring substances in various aquatic environments may provide a source of infection for susceptible fish inhabiting these environments.