The modulus hardening mechanism for yield strength enhancement in multilayer materials is theoretically investigated. The multilayer composition profile used in the analysis has a general trapezoidal shape with allowance for two different layer thicknesses and two interface widths. The image force method is used to determine effective stresses on dislocations in the multilayer structure. Analytical expressions are derived for the effective stresses in terms of the shear elastic moduli. Calculations are carried out for representative composition profile shapes. It is found that the dislocation experiences the maximum effective stress when it is in the interface between layers, and that the effective stress increases dramatically with decreasing interface width. However, the effective stress is not strongly affected by either the multilayer wavelength or the relative thickness of the layers.