Colletotrichum gloeosporioides secretes a phytotoxic compound that causes anthracnose in Hevea brasiliensis : as a first step we attempted to follow mycelium growth, pH and toxin production by this fungus. The compound was isolated and partially purified by ultrafiltration, acetone precipitation and affinity and gel-permeation chromatography. Material purified was largely carbohydrate with a small protein fraction, Galactose, mannose and rhamnose were the neutral sugars encountered, and serine and threonine the major amino acids found. We propose a molecular mass for this substance of 50333 Da.