Macroconidia ofSporidesmium sclerotivorum, a mycoparasite ofSclerotiniaspp., were induced to germinte by aqueous and ethanolic extracts of sclerotia ofSclerotinia minor. Paper chromatography of sclerotial extracts indicated the presence of several amino acids and carbohydrates, chiefly glucose. Glucose was identified as the principal germination stimulant in ethanolic extracts. Glucose, fructose, mannose, cellobiose, sucrose, maltose, trehalose, soluble starch, and glycerol at 0.1% (w/v) stimulated macroconidia to germinate in 3–6 days at 25 °C. Crude sclerotial extracts, and glucose combined with inorganic and organic nitrogen sources, supported germination of greater numbers of macroconidia than glucose alone. Yeast extract, Casaminc acids, peptone, and several carbon substrates alone did not support germination. Macroconidia germinated well (> 30%) over the range of pH 3–7; maximum germination (> 80%) occurred at pH 5.0–5.5. Mycelial growth in a glucose – Casamino acids - mineral salts medium was also greatest in the range of pH 5.0–5.5, but growth fell off sharply below pH 4.5 and above pH 6.0. The fungus grew slowly on several complex agar media adjusted to pH 5.5.