The current work provides a description of the ice jam phenomena along the river of Bistrita, which has the longest mountainous course in Romania (216km). During the cold season of the year, in the upstream of the Izvoru Muntelui Reservoir over a length of 25-30 km, there are generated with a almost yearly frequency ice blocks accumulations known as ice jams. Analysis of the hidroclimatical and morphological conditions of the river bed has revealed that they are favorable to formation of ice jam provided there is present a certain combination of their temporal variations. Hidraulic geometry of the Bistrita river bed is favorable to flow of frazil slush, frazil pans and ice floes while the air temperature is -7 oC as long as the level of Izvoru Muntelui Reservoir is below 500 m. Over this level, the river bed is blocked with ice jam during the submerse phase of the lake and this blockage advances upstream with velocities of several hudreds of meters per day. The most dramatic phenomena has been recorded during the winter of 2002-2003 when the thickness of the ice was of 6 meters and it caused floods that provoked damages and claimed human lives. Aparition in 2003 of the Topoliceni Reservoir, placed 6 km upstream of the Izvoru Muntelui Reservoir, has complicated the evolution of the phenomena, the lake itself acting as an accumulation pool for the ices in the upstream.