To improve history-taking of infants with suspected gastroesophageal reflux, we developed an Infant Gastroesophageal Reflux Questionnaire consisting of 161 items covering demographics, symptoms (regurgitation, weight deficit, respiratory difficulties, fussiness, apnea, and pain or bleeding of esophagitis), and possible causes (feeding volume and frequency, allergy, infection, colic, central nervous system abnormalities, positioning, and smoke exposure). The questionnaire was completed by primary caretakers of 69 infants aged 1 to 58 weeks suspected of having reflux. Median time to complete the questionnaire was 20 minutes. The median internal consistency of 29 pairs of redundant questions was 0.94. Median test-retest consistency of 110 items for nine respondents was 0.88. Median interobserver consistency, evaluated for 129 items in 35 questionnaires also filled out by secondary caretakers, was 0.85. The median accuracy of four externally validated items was 1.00. This questionnaire can aid pediatricians in making decisions regarding diagnoses and treatment in this common but complex disorder.