Cepacidine A is a potent antifungal antibiotic produced by Pseudomonas cepacia AF 2001. The compound was isolated from the fermentation broth with 1 vol isopropyl alcohol, followed by the collection of the precipitation formed upon concentration of the extract. Purification was effected by chromatography on Diaion HP-20, alumina and reversed phase C18 followed by TLC on silica gel. These techniques afforded the two closely related compounds, cepacidine A1 and cepacidine A2. A mixture of these two compoundscalled cepacidine A, showed high in vitro antifungal activity against the various animal and plant pathogenic fungi. The activity was diminished by the presence of serum. No antibacterial activity was demonstrable.