Template-fixed β-hairpin peptidomimetics of the general formula wherein Z is a template-fixed chain of 12 α-amino acid residues which, depending on their positions in the chain (counted starting from the N-terminal amino acid) are Gly, or Pro, or of certain types which, as the remaining symbols in the above formula, are defined in the description and the claims, and salts thereof, have the property to selectively inhibit the growth of or to kill microorganisms such as Pseudomonas aeruginosa. They can be used as disinfectants for foodstuffs, cosmetics, medicaments or other nutrient-containing materials, or as medicaments to treat or prevent infections.These β-hairpin peptidomimetics can be manufactured by processes which are based on a mixed solid- and solution phase synthetic strategy.