Three new metabolites, microphycin AL828, microguanidine AL772, and microginin AL584 and three known metabolites, anabaenopeptin F, oscillamide Y, and microcin SF608 were isolated from the extracts of a Microcystis sp. bloom collected in Alonim reservoir, Valley of Armagedon, Israel. The planar structure of the compounds was determined by homonuclear and inverse-heteronuclear 2D-NMR techniques as well as high-resolution mass spectrometry. The absolute configuration of the asymmetric centers of the amino acids was studied using Marfey's method for HPLC.