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The Olympic Peninsula, Washington, USA, currently holds 184 alpine glaciers larger than 0.01 km(2) and their combined area is 30.2 +/- 0.95 km(2). Only four glaciers are >1 km(2) and 120 of the others are <0.1 km(2). This represents a loss of 82 glaciers and a 34% decrease in combined area since 1980, with the most pronounced losses occurring on south-facing aspects and in the more arid northeastern part of the range. Annual rate of loss in glacier area for seven of the largest glaciers accelerated from 0.26 km(2) a(-1) (1900-80) to 0.54 km(2) a(-1) (1980-2009). Thinning rates on four of the largest glaciers averaged nearly 1 m a(-1) from 1987 to 2010, resulting in estimated volume losses of 17-24%. Combined glacial snow, firn and ice melt in the Hoh watershed is in the range 63-79 +/- 7 x 10(6) m(3), or 9-15% of total May-September streamflow. In the critical August-September period, the glacial fraction of total basin runoff increases to 18-30%, with one-third of the water directly from glacial ice (i.e. not snow and firn). Glaciers in the Elwha basin produce 12-15 +/- 1.3 x 10(6) m(3) (2.5-4.0%), while those in the Dungeness basin contribute 2.5-3.1 +/- 0.28 x 10(6) m(3) (3.0-3.8%).