At present, protease inhibitors are one of the most studied natural substances. They represent a very heterogeneous group for which uniform rules for their classification have not yet been established. Protease inhibitors occurring in potato tubers can be classified in two ways: according to general classification of protease inhibitors or specific classification for protease inhibitors from potato tubers. Attention is devoted to protease inhibitors especially for their potential use in plant protection and medicine. Potato-tuber protease inhibitors are active against some insect pests such as larvae of genus Diabrotica. In medicine, they can be active in treatment of cancer, dermatitis and obesity.