Antibacterial agents are synthetic compounds that kill or prevent the growth of bacteria. They exhibit selective toxicity to bacterial cells either because they inhibit a biochemical target present solely in bacteria or because they exhibit greater affinity for the bacterial target than the mammalian counterpart. Antibacterial agents are used in the treatment and/or prevention of infections due to pathogenic bacteria in humans and animals. The search for synthetic antiinfective agents began in the early 1900s with Paul Ehrlich's pioneering research on organoarsenicals. Currently, five classes of synthetic antibacterial agents are marketed for therapeutic use: the antitubercular agents, nitrofurans, oxazolidinones, quinolones, and the sulfonamides and combinations. Taken as a whole, drugs from these classes are used to treat a broad range of bacterial diseases, including tuberculosis, urinary tract infections, respiratory tract infections, and infections due to multidrug‐resistant bacteria. Emergence of resistance has limited the usefulness of the antitubercular agents and sulfonamides as sole therapy. The nitrofurans and the oxazolidinones have found their own niches, principally in the treatment of urinary tract infections and serious gram‐positive infections, respectively. The quinolones, by virtue of their broad spectrum of antimicrobial activity, oral bioavailability, good tissue distribution, and well‐understood safety profile, retain a prominent position in the armamentarium of antibacterial drugs.