Virus adsorption to soils is considered to be the most important factor in removing viruses after land treatment of wastewater. Most of the studies on virus adsorption to soils have utilized poliovirus as the model system. In the present study, comparative adsorption of a number of different types and strains of human enteroviruses and bacteriophages to nine different soil types was studied. Under the experimental conditions of this study, greater than 90% of all viruses adsorbed to a sandy loam soil except echovirus types 1, 12, and 29 and a simian rotavirus (SA-11), which adsorbed to a considerably lower degree. A great deal of variability was observed between adsorption of different strains of echovirus type 1, indicating that viral adsorption to soils is highly strain dependent. Of the five phages studied, f2 and OX174 adsorbed the least. In addition to being dependent on type and strain of virus, adsorption was found to be influenced also by type of soil. Thus, soils having a saturated pH of less than 5 were generally good adsorbers. From these results, it appears that no one enterovirus or coliphage can be used as the sole model for determining the adsorptive behavior of viruses to soils and that no single soil can be used as the model for determining viral adsorptive capacity of all soil types. Land application of sewage sludge and effluent for recycling of resources as well as abatement of pollution is being practiced in about 1,000 communities in the United States today (17). This kind of use is expected to increase after the passage of Public Laws 92-500 and 95-217. Since secondary treatment of sewage does not remove all viruses present in domestic sewage (12, 15), it is necessary to determine the fate of viruses after the application of wastewater on land. Factors affecting virus removal during land treatment of wastewater, such as adsorption to soils, have not been studied extensively, and little is known about the fate of human viruses applied to soil. If viruses are not retained by the soil, they may migrate vertically, resulting in groundwater contamination. Enteroviruses have, in fact, been found in groundwater after land treatment of wastewater (26-29).