A total of 448 episodes of bacteremia due to gram-negative organisms observed during the 7-year period between 1983 and 1989 at Hacettepe University Hospitals were studied for evaluating the factors influencing the prognosis. The overall mortality rate was 45.0%. The mortality rates were not significantly different in "rapidly fatal" and "ultimately fatal" disease groups (48.3% and 45.5%, respectively), whereas it was significantly less (34.8%) in the "nonfatal" disease group compared with the "rapidly fatal" category. There were great differences in the mortality rates among different diseases within the same disease category. Shock, multi-organ failure, source of infection, hospital service, appropriateness of antibiotic therapy, and place of acquisition of infection were found to affect prognosis significantly in multivariate analysis. In conclusion, the identification of prognostic factors is a further step for making necessary interventions in reducing the mortality rate associated with bacteremia due to gram-negative organisms. Underlying disease is still an important prognostic factor; however, a new approach is needed for classification of underlying diseases.