The basic problems associated with the transition to supercritical coolant pressure in water cooled reactors are outlined: the need for deeper study of the heat and mass transfer, especially that occurring during flow in complicated spatial structures, in order to develop reliable computational methods and materials for fuel-element cladding that are capable of operating at elevated temperature under the conditions of high corrosion activity of the medium; securing an acceptable degree of safety and increasing the economic efficiency of NPP with a reactor with supercritical coolant pressure.