|| An elicitor of pisatin accumulation was isolated and partially characterized from spore germination fluid, mycelial extract, and cell wall preparation of a pea pathogen, Mycosphaerella pinodes. The elicitor was found to be a polysaccharide or glycoprotein and the active component was composed of glucose. The approximate molecular weight was 70,000 daltons. This elicitor elicited pisatin accumulation in pea leaves at a concentration of 10 ug/ml and the maximum activity was ca. 350-400 ug/ml, but did not elicit phytoalexins in soybean, bean, and red clover. High molecular weight preparations from the mycelial extract and mycelial wall of Mycosphaerella melonis and Stemphylium sarcinaeforme, nonpathogens of pea, elicited pisatin accumulation in pea leaves.