Six brominated pyrrole carboxylic acids, (3), (4), and (8) to (11), have been isolated and identified from an Australian marine sponge,Axinellasp. the structures of four new metabolites, (8) to (11), were secured by derivatization, spectroscopic analysis and synthesis. Two of these, (10) and (11), represent the first reported examples of naturally occurring tribromopyrrole carboxylic acids. the antibiotic properties of the natural products and synthetic analogues are presented. A revision of the structure of a known monobromopyrrole marine natural product, from (6) to (7), is also described.