Internal nutrient load of freshwater bodies is a key element in the study and modeling of the processes of eutrophication of lakes and storage reservoirs. A brief review of the main methods for determining the internal nutrient load of water bodies is presented. All the applied methods are divided into experimental and computational. The experimental methods include direct laboratory determination of fluxes at the water-sediment interface and determination of the internal load using the balance of nutrients in the hypolimnion. The prevalent group of computational methods is estimates of nutrient fluxes from bottom sediments based on the calculation of the external balance of nutrients in the water body. This category of methods also includes estimates of substance fluxes from bottom sediments based on the determination of substance content in different layers of bottom sediments. A separate group considered is attempts to use empirical dependencies to assess the internal load. The most promising methods for estimating the internal load are the methods of mathematical modeling of intrabasin processes. Examples of nutrient load calculations are given. The strengths and weaknesses of each of the presented methods are highlighted.