Two new cytotoxins have been isolated from a species of marine cyanobacterium belonging to the genus Symploca that was collected in Guam. These new compounds, micromide (1) and guamamide (2), were accompanied by the known lipopeptides apramides A (3), B (4), and G (5). The planar structures of both alkaloids were elucidated by standard 2D NMR techniques, and the configurations of the amino acid-derived units in 1 were determined by chiral HPLC. The stereochemistry of the beta-methoxyhexanoic acid in 1 was determined by derivatization with methyl d-mandelate, after acid hydrolysis, and comparison with synthetic standards.