Extensive hydrographic surveys were conducted in Shelikof Strait in March and October 1985. The data are used to describe circulation and property distributions and the changes that occurred. The upper layer flows to the southwest throughout the year, but greatest speeds occur in the fall when surface waters are least saline because of a maximum in freshwater discharge. The deep water has its source to the south, and the properties seem to result from vertical mixing of this southern water. Thus Shelikof Strait has an estuarine-like circulation with a northward, deep inflow. Property distribution showed that isolines were usually deepest on the right side of the channel looking to the southwest; greatest baroclinic speeds were often there also. Differential Ekman pumping may contribute to the development of this structure and its changes. Volume transport estimates varied considerably. In October the southwest flow bifurcated, with part continuing along the Alaska Peninsula and the rest exiting the main channel to the south; in March all upper-layer flow followed the main channel. Shelikof Strait appears to be a system influenced by both density-driven and wind-driven effects.