An understanding of the action of the helical antimicrobial peptide magainin II has significance clinically, since the peptide has broad spectrum antimicrobial, tumouricidal and antifungal activity through its ability to create pores in membranes. To better understand the mechanism of action of this peptide, a joint approach of simulations and experiment was used to determine the factors involved in pore formation by magainin II. Previous studies involving a cysteine-crosslinked mutant indicated that dimerisation of magainin II may be a key step in the insertion mechanism, and atomic detail molecular dynamics simulations have supported the theory that this is due to an inability of the membrane to accommodate the larger bulk of a parallel dimer without significant distortion.