Arbuscular mycorrhizal fungi (AMF) are ancient Zygomycetes forming the most widespread plant-fungus symbiosis. The regulation of this association is still poorly understood in terms of the communication between the two partners. Compounds inside the root and released by the root, such as flavonoids, are hypothesized to play a role in this plant-fungus communication, as already demonstrated in other symbiotic associations (e.g. Rhizobium-leguminoseae). Here we give a general overview of the research concerning this question.