New cyclic hepta- and octapeptide, agardhipeptins A (1) and B (2), were isolated from the cyanobacterium Oscillatoria agardhii (NIES-204). The structures of 1 and 2 were elucidated to be cyclo(-HisJ-Gly2-Trp3-Pro4-TrpS-Gly6-Leu 7-) and cyclo(-Trpl-Leu2-Pro3-Trp4-Ala~-Pro 6-Trp7-ValS-), respectively, by extensive 2D NMR data and chemical degradation. Agardhipeptin A (1) inhibited plasmin with an IC5o of 65 I, tg/mL but agardhipeptin B (2) had no inhibitory activity.