Lake Superior current and temperature data collected during the summer of 1966 and 1967 are combined to provide a description of the summer circulation and temperature structure. Data are largely from the central part of the lake, between the Keweenaw Peninsula and Isle Royale. Circulation and temperature patterns appear to be closely interrelated. Infrared surface temperature patterns from eight flights between July 7 and October 1, 1966, trace the formation of the epilimnion and indicate nearshore packing of surface isotherms along the southern shore of the lake in early summer. Bathythermograph temperature cross-sections from five cruises during the summer of 1967 indicate sharply sloping isothermal surfaces north of the Keweenaw Peninsula in early summer and a well defined thermocline established by early August.