Pore-forming toxins are virulence factors produced by a great variety of pathogenic bacteria ranging from the Gram-positive Staphylococcus aureus to the Gram-negative Helicobacter pylory. The recent studies reviewed in this volume describe the progress that has been made in dissecting the different steps of the mode of action of these proteins which generally include binding to specific cell surface receptors, oligomerization into ring like structures and membrane perforation.