Survival of a single strain E. coli serotype O157:H7, isolated from milk in Poland, was examined in water environment (water, bottom-shore sediments and in muddy water over sediments) at 6°C and 24°C. Pathogenic bacteria were not detected (direct plating method) in water within 32 and 51 days of incubation at 6°C and within 21 and 32 days of incubation at 24°C (except water from one of the rivers, where the disappearance of serotype O157:H7 was noticed only after 54 incubation days). The target bacteria survived in muddy water 49-65 days at 6°C and 26-60 days at 24°C. Bacteria died at the slowest rate in bottom-shore sediments. The disappearance of the enterohemorrhagic serotype in these environmental materials was noticed only after 73-100 (6°C) and 30-60 (24°C) incubation days. The obtained results evidently indicate the existence of possible hazards connected with relatively long survival periods of pathogenic bacteria in water environment. The bottom-shore sediments in particular can be a reservoir of this bacteria.