During the past 2 decades aminoglycosides, penicillins and cephalosporins have been used extensively and this is inevitably associated with the development of antibiotic resistance in some strains of bacteria. Imipenem- cilastatin, aztreonam and the fluoroquinolones seem attractive alternatives, which, when assessed in several trials, fulfilled the expectations as far as efficacy was concerned. However, the use of imipenem was associated with considerable nausea and vomiting, whereas the moderate activity of quinolones against Gram-positive pathogens limits their potential uses. The data on aztreonam are too scanty to allow definite conclusions. The use of the expensive drugs vancomycin or teicoplanin ab initio does not appear to be warranted, because such a strategy does not ultimately contribute to the likelihood of cure in the majority of patients, with the exception in institutions where there is a high prevalence of methicillin-resistant Staphylococcus aureus. They should be reserved for cases with a proven or high likelihood of infection by resistant Grampositive bacteria.