Between 1983 and 1988 we observed altogether 222 cases of neonatal septicemia and/or meningitis in our Department of Neonatology. The incidence was 8.46 per 1,000 liveborn infants. The case fatality rate amounted to 45.9%. The most frequently isolated causative agents were Escherichia coli (23.4%) followed by group B Streptococci (16.7%), Staphylococcus aureus (9.9%), Klebsiella pneumoniae species (8.8%), Serratia marcescens (7.9%), Pseudomonas aeruginosa and coagulase-negative Staphylococci each 5.9%. The report includes information about serotypes of Escherichia coli, group B Streptococci and plasmid patterns of Serratia marcescens. The latter was responsible for an outbreak of septicemia and meningitis with high mortality. The changing infection pattern reflects changes in the newborn population, especially in the patient structure of the neonatal intensive care unit, changes in the antibiotic policy and organizational problems.