Treatment of nosocomial infections costs 11 billion dollars annually in the U.S. alone. About half of these infections are related to medical devices that are implanted in patients for different lengths of duration. Device-associated infections are chronic with considerable morbidity and mortality. According to the Centers for Disease Control and Prevention, there are more than one million such cases annually in the U.S., which result in more than 45,000 deaths. It is well documented that the microbes causing device-associated infections are attached to surfaces and grow in biofilms, which are highly hydrated structures comprised of a polysaccharide matrix secreted by the bound microbes. Biofilm cells are up to 1000 times more tolerant to antimicrobials and disinfectants compared to their free-swimming counterparts. Thus, antibiotics can only eliminate planktonic cells and the symptoms reoccur upon the release of cells from biofilms. With the important roles that biofilms play in device-associated infractions and the unsatisfactory efficacy of antibiotics in treating such infections, it is important to develop new methods to control biofilm formation. Previous discoveries have shown that brominated furanones from marine red alga, Delisea pulchra, have remarkable activities against the colonization of bacteria. Recently, we reported the structural effects of several new furanones on Escherichia coli biofilm formation . In this study, we compared the effects of these furanones on biofilm formation of the human pathogen Pseudomonas aeruginosa and the quorum sensing based on AI-2.