A review is given of the phenomenon of glacier outburst floods. Geographical distribution, modes of occurrence of glacier-dammed lakes and modes of lake-emptying are discussed. Techniques of monitoring the filling and emptying of glacier-dammed lakes are evaluated and procedures for forecasting the magnitude and frequency of floods are analyzed. The histories of floods on the Salmon River (British Columbia/Alaska) and the Donjek River (Yukon) are given as examples.