The Troll and Jotun thermal springs of northern Svalbard, with temperatures of up to 25.6 degrees C, are derived from a major fault forming the junction between Devonian sandstones and Proterozoic marbles, mica schists and gneisses. The Troll waters are dominated by Na-HCO3 compositions and the Jotun waters by Na-Cl compositions. The ＇pristine＇ thermal water source has a sub-neutral pH and is highly reducing. Taken at face value, common geothermometers suggest temperatures at depth of 130-180 degrees C for the Troll springs (corresponding to a depth of 1.6-2.3 km), with 10-30% thermal water diluted by 70-90% cold water. Such geothermometers may, however, be inappropriate to the cool, high CO2 waters of Bockfjord, and real temperatures at depth and dilution factors are probably considerably lower. The salinity of the thermal water appears to be only partially derived from water-rock interaction; Br/Cl ratios suggest that seawater or possibly evaporites may be a source of chloride salinity.