A two-dimensional, four-layer numerical model of tidally induced residual flow is used to quantify longitudinal transport through the interior of Indian River lagoon, on Florida's Atlantic coast. Water depths and surface slopes at the approximate midpoint between two inlets are calculated by assuming that the tide in the interior of the lagoon is the superposition of exponentially damped sine waves representing six tidal constituents. Tidal waves moving south from one inlet are modified significantly by the same six constituents moving north from a second inlet. The net slope as they pass through each other at the study site quantifies the barotropic pressure gradient. Tidal period variations in longitudinal flow are simulated as a response to the barotropic pressure gradient, vertical eddy viscosity, and horizontal and vertical advective accelerations. The model is tuned and simulations are verified by comparing amplitudes and phase angles with values computed from currents and water levels measured over a 65-day study period in the summer of 1981. Results indicate a depth-averaged tidally induced residual flow of 0.8 cm/s at the study site. The residual flow varies from 0.1 to 1.2 cm/s over a synodic lunar month. Just under two thirds of the total is explained by Stokes transport; Eulerian mass transport contributes slightly more than one third. The total mass transport residual current through individual layers decreases from 1.0 cm/s in the top layer to 0.6 cm/s in the lowest 75 cm. An analysis of individual terms in the momentum equation indicates that the force balance is dominated by the barotropic pressure gradient and vertical eddy viscosity forces. The significance of tidally induced residual flow lies in the baseline level of transport it provides at times of low wind speeds. ¿ American Geophysical Union 1990