Plastic rocks can creep, therefore the knowledge of the rheological properties of the drilled formations is an important element of the drilling process and when choosing borehole designs. These properties of plastic formations also influence the way in which appropriate drilling technology and drilling mud properties are selected. The article presents the effect of basic rheological parameters of salt from the Fore-Sudetic Monocline deposit on the drilling of boreholes in the mining area of KGHM Polska Miedź, which in the future can be used as a good drilling practice to improve the safety and efficiency of drilling. The process of drilling in plastic rocks may be hindered. Salt is a plastic rock and in the analyzed rock mass it is deposited at a considerable depth. The caprock exerts big loads on it, beside the temperature in the deposit intensifies the rheological properties of the rock. The creep process causes that the borehole contracts, therefore the knowledge about the rheological properties of the drilled rock is very important for establishing the safe time in which the well may remain uncased. The paper is devoted to the influence of basic rheological parameters of salt bed in the Fore-Sudetic Monocline on the process of drilling of a borehole in the area of KGHM Polska Miedź as these data can be used in drilling practice in the future.