The use of beta-lactamase inhibitors in combination with a beta-lactamase-susceptible antibiotic is a useful strategy to rescue otherwise good antibiotics from failure. However, recent years have seen a rise in the numbers of beta-lactamases that are insensitive to the available beta-lactamase inhibitors. This review summarizes of the mechanisms of action of the principal types of inhibitors and the ways in which beta-lactamase are thought to develop resistance towards them. Ten general classes of inhibitors are reviewed, especially those of therapeutic importance (clavulanic acid, penam sulfones and carbapenems). Copyright 2000 Harcourt Publishers Ltd.