We have examined the protective effect of liquorice or its derivatives against gastric ulcer induced by aspirin. A granular mixture of aspirin alone and coated with liquorice or its derivatives including the deglycyrrhized form, a high glycyrrhized form, carbenoxolone, and enoxolone were studied. Aspirin coated with liquorice reduced the number and size of ulcers, reducing the ulcer index from 1.5 +/- 0.12 to 0.5 +/- 0.12 and the incidence from 96% to 46%. Coating with derivatives was less effective (ulcer index, 0.70-0.94; incidence 62-76%).