An expression for the disadvantage factor for a two-region heterogeneous cell in plane geometry has been obtained within the structure of one-speed neutron transport theory. The scattering in the fuel region has been assumed isotropic; however, to describe more accurately the scattering in the moderator, a two-term kernel has been used. The analysis is based on Case's normal-mode expansion technique and leads to a set of Fredholm equations for the unknown expansion coefficients. Numerical solutions, obtained by solving iteratively the Fredholm equations for the expansion coefficients, are given for several sets of parameters.