A numerical model for one-dimensional virus transport in homogeneous, unsaturated porous media was developed. The model accounts for virus sorption onto liquid-solid and air-liquid interfaces as well as inactivation of viruses suspended in the liquid phase and viruses attached at both interfaces. The effects of the moisture content variation on virus transport in unsaturated porous media were investigated. In agreement with previous experimental studies, model simulations indicated that virus sorption is greater at air-liquid than liquid-solid interfaces. Available data from experiments of colloid transport through unsaturated columns were successfully simulated by the virus transport model developed in this study. ¿ 2000 American Geophysical Union