The invention is concerned with the new use of known catechol derivatives of the formula ##STR1## wherein R.sub.1 and R.sub.2 are each hydrogen, alkyl having 1 to 4 carbon atoms or alkanoyl having 2 to 5 carbon atoms; X is nitro, halogen or cyano and R.sub.3 is chlorine, nitro, cyano or a radical of the formula ##STR2## wherein R.sub.4 is hydrogen, cyano, alkyl having 1 to 4 carbon atoms or alkanoyl having 2 to 5 carbon atoms and R.sub.5 is cyano, alkanoyl having 2 to 5 carbon atoms, hydroxyalkyl having 1 to 4 carbon atoms, carboxyl or phenylcarbonyl unsubstituted or substituted with one to three methoxy groups or pharmaceutically acceptable salt thereof. The new use is the treatment and prophylaxis of ulcers and lesions in the gastrointestinal tract.