Four novel cyclolipopeptides, glycinocins A to D, were isolated from the fermentation broth of an unidentified terrestrial Actinomycete species. These compounds were separated and purified from the fermentation broth by 1-butanol extraction, followed by repeated reversed-phase HPLC. Their structures were elucidated by spectroscopic and chemical degradation studies. The absolute configuration of the amino acid residues was determined using Marfey's methodology. The glycinocin antibiotics are structurally related to amphomycin that was originally reported as a linear lipopeptide with C-terminal diketopiperazine moiety. Our degradation study of the glycinocin antibiotics also yielded diketopiperazine-containing fragments, but these have been shown to be hydrolytic by-products generated by condensation of the pipecolinic acid and diamino propionic acid residues.