Three groups, each of forty children aged less than five years and prepared for elective surgery, had their gastric contents' volume and pH measured. The control group showed an incidence of 67-5 per cent with high acidity (pH equal to or less than 2-5). In the second and third groups magnesium trisilicate mixture was given within thirty minutes prior to induction of anaesthesia. The second group, sampled after induction of anaesthesia, showed a marked reduction in acidity, while the third group, sampled at the termination of anaesthesia and surgery, demonstrated that in most cases the neutralization of gastric acidity was still effective.