Mass transfer from entrapped nonaqueous phase liquids (NAPLs) at subsurface locations of environmental contamination typically takes place in three-dimensional groundwater flow fields. Yet most laboratory studies of NAPLs dissolution have been one-dimensional, eliminating more realistic conditions such as the heterogeneous distribution of entrapped NAPL ganglia and the potential for flow bypassing due to reduced water permeability in contaminated zones. In this study, experiments in two-dimensional flow fields were used to evaluate the effects of flow dimensionality on NAPL dissolution. Modifications of the transport code MT3D provided the capability to simulate NAPL dissolution. Regression analysis, matching experimental observations to simulated predictions, provided parameter values for a proposed phenomenological model of dissolution in two-dimensional flow fields. The proposed model predicted lower NAPL dissolution rates relative to models developed on the basis of published one-dimensional experimental measurements. The results indicate potential for significant errors using the one-dimensionally based models for NAPL dissolution in field applications. ¿ 2000 American Geophysical Union