One hundred inpatients scheduled for elective surgery were studied to determine the age-related risk of pulmonary aspiration as indicated by gastric acidity and volume. Twenty-five patients from 6 months to 12 years old were included in the pediatric age group, 50 patients from 18 to 64 years old were included in the adult age group, and 25 patients older than 65 years old were included in the geriatric group. Mean gastric pH was 1.99, 2.40, and 3.32 in the pediatric, adult, and geriatric age groups, respectively; the differences between the three groups were statistically significant. The proportions of patients with pH less than or equal to 2.50 were also significantly different among three groups: 92%, 76%, and 60% in the pediatric, adult, and geriatric age groups, respectively. Mean gastric volumes were 0.49, 0.37, and 0.24 ml/kg and proportions of patients with volumes greater than or equal to 0.40 ml/kg were 60, 32, and 12% in pediatric, adult, and geriatric patients, respectively. Gastric contents with both pH less than or equal to 2.5 and volume greater than or equal to 0.4 ml/kg were seen in 60, 28, and 12% in the three respective groups. Risk of acid aspiration pneumonitis theoretically is present in all age groups, with children being at greatest risk and geriatric patients with least risk. We have also noted a correlation between age and gastric contents because gastric acidity and volume both decreased as age increased. Increasing length of fasting period increased gastric acidity without significant effect on volume.