A sponge of the lithistid family Theonellidae from southern Mozambique contained the known compound aurantoside A (1) together with two new cyclic peptides, mozamides A (2) and B (3). The structures and absolute configurations of mozamides A and B, which contain a rare ureido group, were determined by interpretation of spectral data and chiral GC-MS analysis of the amino acids resulting from acid-catalyzed hydrolysis.