SUMMARYCunninghamella echinulatahas the ability to utilize each even-chain fatty acid from acetate to stearate, and each odd-chain acid tested, as a sole source of carbon. Intermediates of theβ-oxidation pathway have been isolated from cultures of this organism grown on the various fatty acids. Acetic, butyric, caproic, caprylic, capric, lauric, and myristic acids have been identified from extracts of cultures grown on palmitate. Extracts of laurate-grown cultures were found to contain acetic, butyric, caproic, and capric acids. Butyric and acetic acids were detected in relatively large amounts in caproate-grown cultures; in addition, 2-hexenoic and,β-hydroxybutyric acids were also identified. Propionic and valeric acids were detected in extracts of heptanoate-grown cultures. The finding of all the saturated even-chain acids expected from the degradation of palmitate, laurate and caproate, and of both the saturated odd-chain acids expected from heptanoate, clearly supports the successive loss of 2-carbon fragments. Furthermore, the occurrence ofα-β-unsaturated and,β-hydroxy acids in the caproate cultures, combined with the other data, provides convincing evidence for the,β-oxidation of fatty acids by this fungus.