The pathogenic nature of many infectious bacteria is enhanced by their ability to form surfaceassociated, protected communities known as "biofilms." Due to various factors, bacteria in biofilm communities display significantly greater resistance to traditional antimicrobial therapies than their planktonic brethren. This resistance complicates many common bacterial infections, resulting in recurrent ear infections, bacterial endocarditis, chronic lung infection in cystic fibrosis, infectious kidney stones, and surface infection of implanted medical devices. Owing to the serious nature of many biofilm-mediated infections and the near-complete dearth of effective strategies for treating them, efforts are underway to further understand the nature of bacterial infections involving biofilms and to discover and develop effective therapies to combat them. Particularly, several classes of chemical compounds have shown promise in combating biofilms when used in conjunction with traditional antimicrobials. The vast majority of these compounds exert their anti-biofilm properties through disruption of "quorum sensing," a common means of intercellular communication in bacterial communities that allows coordinated expression of virulence factors and facilitates formation of the oft-complex architecture of mature bacterial biofilms. Other new chemical entities are effective against biofilms without necessarily affecting quorum sensing. This review summarizes salient research in the development of effective chemical countermeasures for Gram-negative and Grampositive bacterial infections involving biofilms.