In May 1985, an 800 m multithermistor cable and automatic data acquisition system were installed in an offshore well in the Canadian Arctic Islands. The well, Cape Allison C-47, was drilled by Panarctic Oils Ltd. in 244 m of water during the winter from an ice-strengthened platform. A novel technique was devel- oped to run the cable and electronics package through the marine riser and to land the system in a specially designed cas- ing hanger assembly just prior to rig release. Over most of the following year, temperature data were gathered at four-hour intervals by the subsea equipment and transmitted acoustically through the water to a recording system left on the sea ice. This paper describes the well modifications required, the automatic data acquisition system and the installation procedure.