Two cyclic heptapeptides, rolloamides A (1) and B (2), have been isolated from the Dominican marine sponge Eurypon laughlini. The structures of 1 and 2 were elucidated by a combination of spectroscopic analyses and chemical degradation. Rolloamide A (1), which was found to exist as two distinct conformers in C(5)D(5)N, exhibits growth suppressive activity against a panel of histologically diverse cancer cell lines.