Anabaenopeptins E and F, two new ureido bond-containing cyclicpeptides, were isolated fromthe cultured cyanobacterium Oscillatoria agardhii(NIES-204). The gross structures ofanabaenopeptins E (3) and F (4) were elucidatedby extensive 2D NMR techniques and chemicaldegradation. The absolute stereochemistry of usual amino acids in3 and 4 was determinedby GC and HPLC analyses.