In September 1996 210'000 m3 of glacier ice broke off from the Gutzgletscher which is situated in the north-west face of the Wetterhorn above Grindelwald (Bernese Alps, Switzerland). The ice masses dropped down the 1000 m high rock face and formed two huge powder avalanches. The avalanche debris blocked a road and the air pressure injured 3 people. The avalanche history of the Gutzgletscher is well documented. The second case study we describe is situated below the top of the Grandes Jorasses in the Italian part of the Mont-Blanc massif. In January 1997, a part of the hanging glacier broke off. The time of the event could be predicted by displacement measurements at the front of the hanging glacier. Below the hanging glacier there are huge starting zones for snow avalanches. Because the break off was expected during a period with considerable avalanche hazard, it was assumed that the ice masses could release big snow-avalanches. For that reason we proposed to evacuate the valley below the hanging glacier. The breaking off occurred a few days after the important snowfall, so that the snowpack had stabilized and no snow avalanches were observed. There were no damages. For both cases the Swiss Federal Institute for Snow and Avalanche Research (SLF) prepared hazard maps and worked out corresponding safety plans in collaboration with the Laboratory for Hydraulics, Hydrology and Glaciology (VAW). The main principles and difficulties of hazard assessment for ice avalanches are described based on the two case studies.