Corrosion testing of various metal alloys was carried out down-hole in a high temperature sour geothermal well in Krafla. The tests were done following a failure analysis of a broken liner from the well. The failure analysis revealed that the liner was severely corroded and parts of it situated at 1600 m depth had experienced hydrogen damage in the form of hydrogen embrittlement. The specimens tested were exposed to the down-hole geothermal environment for 4 days and 14 days. Various stainless steels, nickel alloy and carbon steel casing materials were tested. A majority of the materials tested had a decrease in elongation on tensile testing both after 4 days and 14 days in the down-hole geothermal environment. The corrosion rates were above acceptable limits for the carbon steels and the 13Cr stainless steel. The highly alloyed austenitic and duplex stainless steels and the nickel alloy all had corrosion rates below the acceptable limits (0.1 mm/year). The results from the corrosion testing and analysis are described and discussed in this paper.