With the exception of dikaryotization, the complete life-cycle of Ustilago esculenta occurred on potato dextrose agar in culture. In liquid synthetic media, the maximum dry wt of sporidia was reached in 7 days at 27°C compared with 20 days for mycelium. The sporidia were hetero-trophic for thiamine but not for biotin; the mycelium required neither vitamin. Mannitol supported the best growth of sporidia but only poor growth of mycelium; both stages grew well on fructose, glucose and sucrose. At suitable dilutions, an aqueous extract from culms of the host plant supported growth of sporidia and mycelium that was similar, or superior, to that on synthetic media. The implications of these results for the host-parasite combination are discussed.