Abstract: Using monthly precipitation and temperature data from national meteorological stations and a digital vector map of modern glaciers from the Chinese Glacier Inventory,the glacier mass balance and glacier runoff in 1961-2006,in the Hexi Inland River Basin (HIRB),China,are estimated based on a monthly degreeday model and compared with the observed data.The results suggest that the modified monthly degreeday model can simulate the longterm changes in glacier mass balance and glacier runoff.It was found that the mean annual glacier mass balance during 1961-2006 was -49.5 mm per year.In the west of HIRB,the glacier exhibited slight negative mass balance; while glaciers in the east experienced serious mass loss.The average annual glacier runoff was 1.02 billion m 3 in 1961-2006.Over the entire basin,glacier runoff accounts for 14.1% of the total river flow.The prominent glacier runoff occurred in the Shule River and Danghe River,which accounts for 31.5% and 41.7% of the river flow,respectively.The results also show that glacier runoff accounts for 22.9% and 5%-15% of the river flow in Beida River and Heihe River,respectively and Shiyang River was less than 10%.Glacier runoff and its influence on river flow have increased in the last 46 years over HIRB.