Abstract: Two crude elicitor fractions were extracted from mycelia of Marssonina brunnea and itscultural supernatant. The leaves of tobacoo, eggplant and capsicum were treated with the two crude elicitor fractions. Hypersensitive reactions were observed only on the tobacoo when treated with the elicitor fractions, but not on the other two plants. The changes of peroxidase activity of resistant and sensitive poplars after being treated with the two crude elicitor fractions were also studied. The results showed that the activity of peroxidase of resistant poplar was distinctly higher than that of sensitive trees. All these reveal that the two crude elicitor fractions contain elicitor active elements and these elicitors belong to special elicitors.