Until the 1950's Serratia marcescens was generally considered as non-pathogenic for humans. Since then the organism has been reported repeatedly as a cause of nosocomial infections. The major clinical concern about Serratia marcescens is its implication in epidemic infections and its resistance to usual antibiotics causing therapy to be difficult. We report the occurrence of Serratia marcescens as the cause of severe septicemia in three premature infants. Two infants showed a severe course of sepsis, the third infant suffered from additional meningitis and a brain abscess. All infants survived, but only one had no sequela.