Serine protease inhibitory glycopeptides, aeruginosins 205 A (1) and -B (2), were isolated from the cyanobacterium Oscillatoria agardhii (NIES-205). The gross structures of these glycopeptides were elucidated by mass and 2D NMR spectral data. The planar structure of 2 was the same as that of 1 but differed in the stereochemistries of 3-hydroxyleucine (Hleu) and phenyllactic acid 2-O-sulfate (Plas). These glycopeptides are potent inhibitors of trypsin and thrombin.