The effects of preoperative fasting on plasma glucose and gastric emptying was studied in 62 infants aged less than three months after a feed of either breast milk or an infant milk formula. Prior to induction of anaesthesia no infant was hypoglycaemic, defined as plasma glucose less than 2.2 mmol/l. Five per cent of infants had a significant volume of residual gastric contents. The mean intraoperative plasma glucose levels rose significantly and this was not influenced by the use of intravenous Hartmann's solution or low dose opioids. Infants in this age group tolerate three- to four-hour preoperative fasts well as no infant became hypoglycaemic intraoperatively. They demonstrate a hyperglycaemic response to the stress of anaesthesia and surgery, and may not need routine intraoperative glucose supplements although plasma glucose should still be monitored.