Gram-negative infection is a serious complication and a great deal of attention has been paid to it lately. The aa. present 31 cases of gram-negative infection. The most common organisms were Escherichía coli and Klebsiella-Aerobacter (58% of the cases) followed by the Pseudomonas group. Males were more affected than females. In 61,3% of the cases the urinary tract was the site of infection. Previous treatment occurred in several patients the most important being antibioties, steroids and cytostaties. The most frequent predisposing diseases were diabetes mellitus and malignancy. Urinary tract manipulation (with previous infection or wihout it), gastrointestinal surgery and urinary or biliary obstruetion were main precipitants. Chilis, fever and low blood pressure were the most frequent clinicai manif estations. Shock ocurred in 58% of the cases, which is a very high incidence when compared with other statisties. Acute renal insuficiency, super-infection and metastatie lung infection also ocurred. General therapeutic consideralions as well as antibiotic administration schedules are suggested by the authors. Mortality due to simple bacteremia was 30,7%, the association of bacteremia and shock raised this figure to 72,2%. Pseudomonas infection gave 100% mortality.