In analyzing real problems using the classical theory of one-dimensional consolidation it is necessary to make a number of simplifying assumptions, the effects of which cannot be determined easily. The nature of these errors is studied by comparing classical analyses with finite difference analyses that take into account time-dependent loading, large strains, nonlinear stress strain properties, effective-stress dependent properties, hysteresis, settlement dependent submergence, layered soil deposits, and other such phenomena. Finally, classical and finite difference analyses were compared for four field problems ranging from settlement of embankments over stiff and soft clays to consolidation of waste slimes. Although the consolidation times, predicted using classical and finite difference methods, sometimes differed by a factor of ten, it was found that a number of simple adjustments to classical analyses improved correlations significantly, and many of remaining errors tended to counterbalance each other. In many cases uncertainties in soil properties may introduce errors as large as those in the corrected classical theory.