During the last two decades the mortality from gram-negative septicemia in neutropenia patients with serious underlying disease has declined from 85% to less than 20%. Many factors seem responsible for this trend: (a) the development of potent broad-spectrum antimicrobial agents (b) aggressive clinical approaches to empiric therapy entailing the use of antibiotics before results of cultures are known. (c) better supportive care, (d) improved treatment of underlying disease. Controversy persists about the choice of "optimum" regimens: clinical studies to date show major differences in evaluation criteria, particularly in the definition of "response". The largest and most convincing studies of gram-negative bacteremia still favor the use of antibiotic combinations in patients with profound, persistent neutropenia.