Two analogues of the marine natural product bromoageliferin have been synthesized and subsequently assayed for the ability to inhibit the formation of Pseudomonas aeruginosa biofilms. Both compounds inhibited the ability of Pseudomonas aeruginosa strains PAO1 and PA14 to form biofilms; however, they displayed differential toxicity to planktonic bacteria. The cis analogue, CAGE, was found to possess greater toxicity than the trans analogue, TAGE. These compounds have no structural homology to any known inhibitors of Pseudomonas aeruginosa biofilms.