BACKGROUND: Aspiration of gastric contents into the lungs is one of the most feared complications during anesthesia. Various factors combine to make pediatric patients more susceptible to regurgitation and aspiration than adults. We compared the risk of incidence of acid aspiration in two groups, after examining the pH, and volume of gastric contents in pediatric and adult patients. METHODS: This study was carried out with inpatients scheduled for elective surgery under general anesthesia. Sixty patients from 1 to 13 years old were included in the pediatric age group, and sixty patients from 18 to 60 years old were included in the adult age group. After induction of anesthesia and stabilization of the condition of the patient, gastric contents were collected via a 10 - 18 French Salem Sump tube. Gastric volume and pH were measured. RESULTS: The mean gastric volume in the pediatric group was significantly higher than those in the adult group, whereas, The mean gastric pH in the adult group was significantly higher than those in the pediatric group. CONCLUSIONS: We concluded that pediatric patients have a lower gastric pH but a higher gastric volume than adult patients.