Carbohydrates are important but challenging targets for supramolecular chemists. They possess complex, irregular and variable structures, and are strongly attracted to water, their natural environment. This tutorial review describes work on synthetic receptors which bind carbohydrates through non-covalent interactions, mimicking the strategies used in biology. Emphasis is placed on systems which operate in purely aqueous solution, without involvement of organic solvents. Although the problem is difficult, the careful design of complementary cavities can lead to surprisingly good results. In particular, a receptor for glucose has achieved performance which generally matches biology, and augurs well for real-world applications.