Ceratinarnides A and B (1 and 2), new bromotyrosine derivatives, have been isolated from the marine sponge Pseudoceratina purpurea, along with the known psammaplysins A (3) and E (4), ceratinamine (5), moloka'iamine (6), pseudoceratidine (7), and 4,5-dibromopyrrole-2 carbamide (8). Their structures were elucidated on the basis of spectral data. Compounds 1-7 inhibited larval settlement and metamorphosis of the barnacle Balanus amphitrite with ED50 values of 0.10-8.0 gg/mL, while compounds 3 and 8 induced larval metamorphosis of the ascidian Halocynthia roretzi at concentrations of 1.2 and 25 gg/mL, respectively. Compounds 5 and 6 also showed cytotoxicity against P388 murine leukemia cells with IC50 values of 3.4 and 2.1 gg/mL, respectively; 7 was antibacterial against Flavobacterium marinotypicum.