The Rio Grande is one of the main Andean tributaries of the Rio Mamore, a tributary of the Rio Madeira which is the main southern affluent of the Amazon. The use of historical (1969-1990) and unpublished data on sediment transport from 15 Andean gauging stations, made it possible to assess the very strong temporal variability of river sediment-transport. Most of the sediment transport occurs during the three months of high water, which may represent up to 90% of the annual load. An exceptional flow registered on the Rio Pirai during March 1983, supplied a sediment yield 20 times higher than the annual mean value of the 18 previous years. The measured sediment transport rate varies from 190 to 11 600 t km2 year-1. Sedimentation is observed along these Andean rivers, which may represent up to 50% of the total sediment load. -Authors