A detailed study of flow, heat transfer, and pressure drop for louvered fins is presented. Louver-by-louver mass transfer data are acquired for Reynolds numbers from 130 to 1400. Pressure-drop data are obtained using a low-speed wind tunnel and local flow structures are visualized using dye injection in a water tunnel. Particular attention is placed on the role of vortex shedding in heat transfer enhancement. In contrast to recent studies for similar offset-strip arrays, vortex shedding is found to have less impact in louvered-fin arrays. Several practical implications for heat exchanger design and analysis are discussed.