Recently the contamination of water environment involving rivers, lakes, the sources of drinking water, etc. by viruses has been paid attention to as a new threat. The behavior of the viruses found in water environment is not well understood so far. However, it is suspected in general that the viruses are adsorbed onto solid surfaces such as suspended solids and sediment and keep their activities for a long time. Most likely, it is true that the adsorption of the viruses onto solid surfaces is one of the major factors controlling their transport and survival in water environment. In this work, the adsorption equilibrium relations of model viruses in water environment and their activities on solid surfaces were investigated. The E. coli phage such as Qβ, fr, MS2 and T4 were employed for experiments as model viruses, and cellulose and its derivatives, kaolin, carbon black, etc. were chosen as model solid surfaces. All the adsorption isotherms of model viruses on model surfaces were successfully written as the linear expression by the Henry equation in the concentration range of 102-107 [PFU/ml]. The resultant Henry constants were correlated with the total acidity of the solid surfaces. Stability of the model viruses was completely different when they were adsorbed on the solid surfaces and when they were suspended in water. The viruses adsorbed on the solid surfaces were significantly stable compared with the suspended ones regardless of the surface properties. It is suggested that the shrinkage of the virus is one of the important survival factors and the adsorption onto solid surfaces enhances their activities.