The acids of Phycomyces blakesleeanus were studied under a variety of incubation conditions. Forty-six metabolites were identified. Among these were p-hydroxybenzaldehyde, turbinaric acid and phycodioic acid, the last being a new compound. The levels of fumaric, malic, protocatechuic, gallic and turbinaric acids varied, depending on agitation, illumination and age of the culture.