Twentieth-century fluctuations of Icelandic glaciers reflect the climatic transition from the cool climate of the late "Little Ice Age" into the warm climate of the modern era. Changes in the length of six glaciers are compared to instrumental records of seasonal temperature, precipitation, and to the North Atlantic Oscillation (NAO) index. The results indicate that shifts in the location and intensity of the Icelandic Low are associated with the regional retreat and subsequent readvance of the glaciers, but the detailed relationships are complicated by Iceland's location close to the fulcrum of the Greenland-Scandinavia climate "see-saw." In general, decades of cool, cloudy low-NAO index summers following decades of wet winters have caused late-20th-century glacier advances. Much larger glaciers prior to 1920 were favored by low-index summers and winters and generally colder temperatures in all seasons.