During 1985 and 1986, 48 bacteremias due to Enterobacter spp, Acinetobacter spp, Serratia spp or Pseudomonas spp were collected by the SES Group. The mortality rate of those infections due to multiresistant organisms appeared high (27.9%). Among all factors influencing the prognosis, the following, age over 75 years, hospital-acquired infections, occurrence of shock and single antimicrobial therapy, are those associated with a high fatality rate. Given that clinical signs are not specific, nosocomial bacteremias should be treated by antimicrobial agents having wide spectrum, rapid onset of action and most often in combination.