Current, salinity, and temperature data obtained from lower Cook Inlet during May-September 1973 have been analyzed. These data define a regional mean circulation whose main features are (1) a concentrated southward flow along the western shore of lower Cook Inlet of water from upper Cook Inlet which has been diluted by river input, (2) an intense westerly flow across the lower inlet which originates from Kennedy Entrance, exists via Shelikof Strait, and is bathymetrically steered in a cyclonic sense during its transit across the inlet, and (3) a slow northward drift in eastern lower Cook Inlet. The southward flow is an estuarine mode due to freshwater input to upper Cook Inlet. The westerly flow is driven by the westward flowing Alaska Current. The weak northward drift replaces water which has been entrained into the south flowing current. Large tidal and wind-induced currents are superimposed on this mean flow and contribute to complex temperature and salinity distributions. The circulation scheme as redefined here allows for vertical motions and has important consequences in relation to high regional biological productivity and fates of contaminants.