The most common cause of congenital dacryostenosis is the persistence of Hasner's membrane, which in more than 90% of cases perforates during the first 4 to 6 weeks. If no perforation occurs, the tears gather in the lacrimal duct and lacrimal sac until the system is full and an inflammation starts. Formerly, dacryocystitis neonatorum was caused mainly by gram-positive cocci, in particular Streptococcus Pneumoniae; the primary cause now, in consequence of the abuse of antibiotics, are the gram-negative enterobacteriaceae. The most common agent still is Staphylococcus, which is becoming more and more resistant to gentamycin (26.5%). During the past 3 years 64 infants have been examined at the Second Eye Clinic of Vienna University. Smears were taken from the purulent discharge and tested in the usual microbiological way. The study shows the importance of exact diagnosis and specific therapy.