Recent progress in glycobiology has revealed that cell surface oligosaccharides play an essential role in recognition events. More precisely, these saccharides may be complexed by lectins, carbohydrate-binding proteins other than enzymes and antibodies, able to recognise sugars in a highly specific manner. The ubiquity of lectin-carbohydrate interactions opens enormous potential for their exploitation in medicine. Therefore, extraordinary effort is made into the identification of new lectins as well as into the achievement of a deep understanding of their functions and of the precise mechanism of their association with specific ligands. In this review, a summary of the main features of lectins, particularly those found in legumes, will be presented with a focus on the mechanism of carbohydrate-binding. An overview of lectin-carbohydrate interactions will also be given, together with an insight into their energetics. In addition, therapeutic applications of lectins will be discussed.