The era of the "classical antibiotic" may be over. The emergence of resistance has seen to that. Yet no truly novel class of antibacterial agent has come on the market in the past 30 years. Currently there is great interest in peptide antibiotics, especially the cationic peptides. Thousands of such molecules have been synthesised and just a few are entering clinical trials. Because they kill bacteria quickly by the physical disruption of cell membranes, peptide antibiotics may not face the rapid emergence of resistance.