Over the past decade, infections caused by antimicrobial-resistant bacteria have increased and continued to challenge physicians. Recent data show rapidly increasing rates of infection due to multidrug-resistant (MDR) gram-negative bacilli. Furthermore, pandrug-resistant infections now occur, especially due to gram-negative bacilli, and our therapeutic options for these pathogens are extremely limited. Infection caused by MDR bacteria was associated with a greater likelihood of inappropriate antimicrobial therapy, and inappropriate antimicrobial therapy has an adverse effect on survival in patients with serious infections. Consequently, it may be presumed that serious infections caused by MDR bacteria have a worse prognosis because of the delay in initiation of appropriate antimicrobial therapy. Empirical antibiotics for serious infections should be recommended on the basis of the distribution of pathogens and their susceptibility patterns in the institution where the regimen is administered. Therefore, physicians who are caring for patients with bacterial infection should be familiar with local antimicrobial susceptibility patterns and the epidemiology of MDR bacterial infections, in order to improve the treatment outcome of the patients. This comprehensive review aims to describe the epidemiology and clinical implications of MDR gram-negative bacterial infections in Korea, a country with a high prevalence of antimicrobial-resistant pathogens.