Agreement on criteria for defining nosocomial infections is essential when surveillance is intended for quality assurance. The CDC criteria for patients < 12 months old were compared with locally developed criteria for neonates in a 10-month study of nosocomial infections in a Berlin University hospital. Six hundred and seventy-seven neonates were observed prospectively for 11,936 patient days. The overall nosocomial infection incidence rate was 13.2%. Because of the observed strength of agreement between the CDC and local criteria for central line-associated primary bloodstream infections and for ventilator-associated pneumonias (recommended by the NNIS system for inter-hospital comparisons) and the preference of the clinicians for the local criteria, we decided to use the latter for an ongoing surveillance system which nonetheless would retain the possibility for comparison with NNIS-data.