The effect of metoclopramide on gastroesophageal reflux was studied in 30 infants less than 1 year of age. Gastroesophageal reflux was documented in all infants by extended pH monitoring before enrollment in the study. Patients were randomly assigned to receive metoclopramide 0.1 mg/kg or placebo four times a day, 1/2 hour before feeding for 1 week, followed by the alternate regimen for 1 week. The infants were reevaluated with extended pH monitoring and scintigraphy after 4 to 7 days of each treatment. A symptom score was derived by determining the average number of occurrences of all symptoms recorded daily by parents on a symptom checklist during pretreatment, placebo, and metoclopramide treatment periods. There was a difference between pretreatment evaluation and placebo periods with respect to daily symptom scores (p less than 0.005), reflecting a significant placebo response. However, no difference in scintigraphic study was found between placebo and metoclopramide periods. A significant difference between placebo and metoclopramide periods was noted in the percentage of time esophageal pH was less than 4.0 (p less than 0.001). However, although metoclopramide decreased the proportion of time esophageal pH was less than 4.0, pH remained less than 4.0 for more than 5% of the time in most patients. Substratification of the total group into infants younger and older than 3 months revealed that older infants had greater average daily weight gain during the metoclopramide treatment period (34.3 gm/day) than in the placebo treatment period (6.6 gm/day, p = 0.05). We conclude that metoclopramide in the dosage 0.1 mg/kg four times daily reduces reflux in infants and may be useful for infants with poor weight gain and other serious complications of gastroesophageal reflux.