A novel elicitor that induces chitinases in tobacco BY-2 cells was isolated from Alternaria alternata102. Six other fungi, includingA. alternataIFO 6587, could not induce, or weakly induce chitinase activity. The purified elicitor was soluble in 75% methanol and showed the chitinase-inducing activity when applied at concentrations of as low as 25 ngÆmL )1 .