When growth-phase cell suspension cultures of Scutellaria baicalensis were treated with 50 mu g of yeast elicitor preparation ml(-1), both oleanolic acid and ursolic acid transiently increased in the culture medium rather than in the cells. The maximal triterpenoid concentration was 13.7 mg l(-1) media approx. 35 h after treatment, whereas the maximum concentration was 2.1 mg l(-1) media after about 20 h following treatment with methyl jasmonate. Elicitor treatment also doubled phospholipase A(2) activity (25 pmol mg(-1) min) and the simultaneous treatment of aristolochic acid, a phospholipase A(2) inhibitor, inhibited triterpenoids accumulation as well as phospholipase A(2) activity.