A theoretical model has been developed to study the effect of magnetic-field-dependent and anisotropic screenings on the longitudinal resistivity in n-type Hg 0.8 Cd 0.2 Te in the extreme quantum limit at low temperatures, taking into consideration different scattering mechanisms, viz. deformation potential acoustic phonon, ionized impurity, and alloy disorder. Other complexities, such as band nonparabolicity and nonequipartition of phonons, have been included in the calculation. The theoretically obtained values of the resistivity for magnetic-field-dependent and anisotropic screening have been compared with the classical case and also with the experimental results. The agreement with the experimental results improves when the effect of magneticfield-dependent screening is taken into account.