Antimicrobial peptides (AMP's) are promising compounds in the battle against antibiotic resistant pathogens. Many AMP's function by interacting with the bacterial membrane and selectively permeabilizing it. Improvements are desired in the potency and the in vivo stability of the AMP's. Both aspects have been approached by the preparation of multivalent versions of AMP's that contain several copies of the peptide attached to a scaffold or core molecule. Both short and long sequences have been used and in selected cases major increases in antibacterial activity, membrane permeabilization potency and in vivo stability have been obtained.