Disodium edetate (ethylenediaminetetraacetic acid, disodium salt; disodic EDTA), 3 g, was given, via an intravenous normal saline drip of 30 min, to 25 patients in order to assess a benefit for anaesthesia practice. A significant reduction of both volume and acidity of the gastric secretion was found in all the 10 patients with peptic ulcer having received the drug. The peak of the change was 1 h after administration. In other 10 non-ulcer patients undergoing orthopaedic surgeries under epidural anaesthesia with lidocaine 2%, 5 mg kg-1, pH of the gastric juice unanimously rose, from 2.24 +/- 0.28 to 4.10 +/- 0.21 1 h after EDTA with a P derived from paired difference analysis of less than 0.001. A similar group of patients receiving only normal saline showed no important changes in pH (from 2.37 +/- 0.24 to 2.34 +/- 0.19). The pH of the fundic surface, measured directly under fiberscopic control in further 5 patients suffering from peptic ulcer, was found also to rise from 1.84 +/- 0.21 to 4.62 +/- 0.34 1 h after EDTA, P less than 0.001. Total and ionized calcium changed unsignificantly. Disodic EDTA in the dose and manner used in this study showed no clinical side-effects. The constant and obvious effect of inhibition of the gastric secretion as well as the dynamics of such an action recommend disodic EDTA to be tried in reducing the aspiration pneumonia morbidity.