We report a prospective evaluation of the fluorescein disappearance test (FDT) in the diagnosis of lacrimal outflow obstruction in infants under 1 year of age. In a preliminary study of 80 lacrimal systems, we showed that the FDT is a sensitive (90%) and specific (100%) test in aiding the diagnosis of nasolacrimal obstruction in infants. In the main study, we examined 288 eyes of 232 children with epiphora. The FDT was abnormal in 237 (82%). Of the remaining 51 eyes, there was a clinical explanation for this in 33 cases (epiblepharon, conjunctivitis, etc). We have found that this simple and reliable test taken in conjunction with clinical examination provides an objective assessment of the lacrimal outflow status of young children.