Environmental pollution, river regulation and chemical spraying cause habitat destruction. At the time when the noble crayfish used to live in numerous waters in Europe, this was not a key-factor. Nowadays water regulation which is ill-conceived or badly performed may lead to its retreat. The noble crayfish leads a nocturnal lifestyle so it looks for a shelter at a day among the tree roots, water plants, and the burrows. Strengthening and correction of the river banks strongly affect and impoverish its habitat. The noble crayfish is particularly sensitive to the water chemistry changes, and it is frequently called the clean water indicator. Water eutrophication is also very harmful for crayfish habitat. Chemical spraying of fields and forests is also serious threat. Chemical substances, which reach refuges of the Danube crayfish (tailors) are lethal threat for them.