Spatial structure of polypeptide antibiotic polymyxin M in water was studied by one-and two-dimensional (COSY, COSY-45, RELAY) H NMR spectroscopy. Analysis of the signal spectral parameters revealed two intramolecular hydrogen bonds in the cyclic part of the molecule which was analogous to the structure of polymyxin B. However, configuration of both the beta-turns in the polymyxin M structure differed from that of the detected earlier beta-turns in the structure of polymyxin B.