The ability to drink clear liquids without vomiting after anesthesia and surgery is a commonly used criteria for discharge of pediatric day surgery patients. We hypothesized that the ability to drink as a prerequisite for discharge would not affect the frequency of vomiting, delay discharge, or increase the frequency of readmission of children for dehydration after day surgical procedures. We randomized 989 patients between the ages of 1 month and 18.0 yr to one of two groups. The 464 "mandatory drinkers" were required to demonstrate the ability to drink clear liquids without vomiting prior to discharge from the hospital, whereas 525 "elective drinkers" were allowed but not required to drink. Other than the discharge criteria, the patients were managed in an identical fashion; the minimum volume of intravenous fluids received by all patients was adequate to supply a calculated 8-h fluid deficit prior to discharge from the hospital. There were no differences between the two groups in the incidence of vomiting in the operating room, the postanesthesia care unit, or after discharge from the hospital. However, in the day surgery unit, only 14% of the elective drinkers vomited compared to 23% of the mandatory drinker group (P less than 0.001). The mandatory drinkers had a more prolonged stay in the day surgical unit, averaging 101 +/- 58 min (mean +/- SD) compared to 84 +/- 40 min for elective drinkers (P less than 0.001). No patient in either group required admission to the hospital for persistent vomiting on the day of surgery, and no patient required readmission for vomiting or dehydration after discharge from the day surgery unit.(ABSTRACT TRUNCATED AT 250 WORDS)