The continuity equation for electrons in a decaying plasma is solved numerically in three dimensions including a loss term quadratic in the electron density (i.e., two-body electron-ion recombination) and an ambipolar diffusion term. The geometries investigated are the finite cylinder, the rectangular parallelepiped, and some one-dimensional cases. The electron densities are averaged assuming weighting functions corresponding to various microwave probing field distributions (cylindrical TM 010, TE 011, and TE 111 and retangular TE 101 modes) and are therefore directly proportional to measured quantities, such as resonant frequency shifts, obtained in microwave afterglow studies of recombination. Three different initial electron distributions are used, corresponding to a uniform (recombination controlled), a fundamental diffusion mode and a somewhat more spatially constricted distribution. The linear range of the computed (averaged densities) −1-versus-time curves is determined and correction factors are derived which, if applied to the observations, yield the corrected recombination coefficients from the curves. The corrections derived in the two- and three-dimensional analyses are found to be significantly larger than those obtained in the one-dimensional analyses. Also, when considering plasma containers of different shapes but of the same fundamental diffusion length, a larger surface/volume ratio is found to be equivalent in effect to an increased diffusion coefficient in the predicted decays. In most cases of practical interest, though, a much stronger dependence upon the varying probing field distributions is found when different container or cavity dimensions are to be compared. When the present analysis is applied to one-dimensional geometries, recombination corrections in agreement with the results of Gray and Kerr are obtained.