We describe the isolation and structural characterization of a family of antimicrobial peptides related to kassinatuerin-2, from the skin secretion of the African hyperoliid frog, Kassina maculata. All four peptides, designated kassinatuerin-2Ma through Md, are C-terminally-amidated 20-mers with the consensus sequence - FX(1)GAIAAALPHVIX(2)AIKNAL - where X(1)=L/F/V/I and X2=S/N. All four peptides are encoded by precursors of 69 amino acids. Synthetic replicates of all kassinatuerin-2 related peptides displayed a potent inhibitory activity against Staphylococcus aureus with a minimal inhibitory concentration of 16microM, at which concentration, however, they effected 18% haemolysis of horse erythrocytes after 2h. Despite obvious membranolytic properties, all peptides were ineffective at inhibiting the growth of Escherichia coli at concentrations up to 200microM and were relatively ineffective against Candida albicans (MIC 120microM). The kassinatuerin-2 related peptides of K. maculata skin secretion thus possess a discrete antimicrobial and weak haemolytic activity in contrast to the prototype kassinatuerin-2 from the skin secretion of Kassina senegalensis.