The preoperative fast is often an unpleasant preoperative experience that might be alleviated by allowing children to drink clear liquids. The authors compared gastric fluid volume and pH in two groups of children, one of whom was permitted clear liquids until 2 h before surgery (study group) and the other followed routine preoperative fasting orders (control group). The study group was not limited in the quantity of clear liquid allowed with the exception that the last intake prior to surgery was limited to 8 ounces. The study group (n = 53) averaged 5.9 +/- 5 yr and weighed 23.6 +/- 17 kg, while the control group averaged 7.3 +/- 4.6 yr and weighed 29 +/- 17.7 kg (P = NS). Gastric contents were aspirated following induction of anesthesia. Gastric fluid volume averaged 0.44 +/- 0.51 ml/kg for study group and 0.57 +/- 0.51 ml/kg in the control group (P = 0.12). Of the study patients, 48% had a measured gastric fluid volume greater than or equal to 0.4 ml/kg compared with 58% of the control patients (P = 0.77). Eighty three patients had sufficient gastric fluid for pH determination; of these 34/35 (97%) in the study group and 44/48 (92%) in the control group had a gastric fluid pH less than or equal to 2.5. Using a linear analog scale parents rated the children in the study group to be less irritable (P less than 0.001) and to have had a better overall preoperative experience (P less than 0.01) compared with the control patients.(ABSTRACT TRUNCATED AT 250 WORDS)