Pore-forming proteins or peptides (PFP) have now been isolated from a wide array of species ranging from humans to bacteria. A great number of these toxins lyse cells through a ‘barrel-stave’ mechanism, in which monomers of the toxin bind to and insert into the target membrane and then aggregate like barrel staves surrounding a central, water-filled pore. An evaluation of the secondary structures suggests that common secondary structures may be employed by most of these toxic PFP.