Four novel lipopeptide antibiotics, friulimicins A, B, C, and D, were isolated from cultures of Actinoplanes friuliensis HAG 010964 after fermentation in different nutrient media. The new compounds were separated by ion-exchange chromatography from the acidic lipopeptides of the amphomycin type also present in the culture fluid, compounds A-1437 A, B, E, and G. The principal constituent friulimicin B, C59H94N14O19, was structurally characterized by mass spectrometric investigations of its hydrolysis and partial degradation products and by sequencing of the cyclic acyl peptide. The NMR data of friulimycin B and the amphomycin constituent A-1437 B were completely assigned by a variety of 2-D experiments, and confirmed the structures determined by mass spectrometry. All 8 lipopeptides possess an identical peptide macrocycle as their central element, linked via a diaminobutyric acid N-terminal either to an acylated asparagine residue or, in the case of the amphomycin series, to an acylated aspartic acid residue. The structures of the amphomycins have now been revised to take account of the peptide framework described herein and the determined cis-configuration of the exocyclic double bond. As a consequence of their higher isoelectric points, the new compounds friulimicin A, B, C, and D have different properties than the amphomycins.