Antimicrobial resistance of bacteria has become a worldwide problem. Available data suggest that the resistance problem is comparatively more serious in Korea. In large hospitals, the proportion of methicillin-resistant Staphylococcus aureus (MRSA) has been reported at over 70%, and of penicillin-nonsusceptible Streptococcus pneumoniae at around 70%. Infection or colonization of vancomycin-resistant enterococci has started to increase. Extended-spectrum β-lactamase producing Escherichia coli and Klebsiella pneumoniae has become widespread and even carbapenem-resistant Pseudomonas aeruginosa has been increasing. Community-acquired pathogens such as Salmonella, Shigella and Neisseria gonorrhoeae are often resistant to various antimicrobial agents. The prevalence of resistant bacteria can lead to erroneous empirical selection of either noneffective or expensive drugs, prolonging hospitalization and higher mortality. The emergence and spread of resistant bacteria are unavoidable unless antimicrobial agents are not used at all. The high prevalence of resistant bacteria in Korea seems to be related to antibiotic usage: 1) easy availability without prescription at drug stores, 2) injudicious use in hospitals, and 3) uncontrolled use in agriculture, animal husbandry, and fisheries. Nosocomial infection is an important factor in the spread of resistant bacteria. Antimicrobial resistance problems should be regarded as the major public health concern in Korea. It is urgently required to ban the sale of antibiotics without prescription, to use antibiotics more judiciously in hospitals by intensive teaching of the principles of the use of antibiotics, and to establish better control measures of nosocomial infections. Regulation of antimicrobials for other than human use should also be required. These issues are not easy to address and require the collective action of governments, the pharmaceutical industry, health care providers, and consumers.