Several isolates of Stagonospora sacchari causing the leaf scorch disease of sugarcane were found to produce at least two phytotoxins (toxin I and II) in cultures as well as in spore-germinating fluids. Toxin I and II were isolated and chemically determined to be 6-methylsalicylic acid and (+)-epoxydon, respectively. Their threshold concentrations inducing leaf necrosis on susceptible cultivars of sugarcane were 30μg/ml for toxin I and 25μg/ml for toxin II, whereas resistant sugarcanes and many nonhost plants, except maize and sorghum, were more tolerant to the toxins. The toxins caused a rapid increase in loss of electrolytes from leaf tissues. Potassium was the prominent cation species in the leaked electrolytes. There were significant correlations between susceptibility to the leaf scorch and toxin sensitivity with toxin I and II among sugarcane cultivars examined.