During water injection, solid and liquid particles dispersed in the injected water are trapped by the porous medium and may increase hydraulic resistance to flow. The full-length paper presents a mathematic model for deep bed filtration that contains filtration and formation-damage coefficients, lambda and beta. These parameters should be determined from laboratory coreflood tests. A new method to determine both coefficients is developed. The proposed method furnishes unique values for the two empirical coefficients.