As the prevalence of tuberculosis declines, the proportion of mycobacterial lung disease due to nontuberculous mycobacteria (NTM) is increasing worldwide. In Korea, M. avium complex and M. abscessus account for most of the pathogens encountered, whilst M. kansasii is a relatively uncommon cause of NTM pulmonary diseases. NTM pulmonary disease is highly complex in terms of its clinical presentation and management. Because its clinical features are indistinguishable from those of pulmonary tuberculosis and NTMs are ubiquitous in the environment, the isolation and identification of causative organisms are mandatory for diagnosis, and some specific diagnostic criteria have been proposed. The treatment of NTM pulmonary disease depends on the infecting species, but decisions concerning the institution of treatment are far from being easy. It requires the use of multiple drugs for 18 to 24 months. Thus, the treatment is expensive, often has significant side effects, and is frequently not curative. Therefore, clinicians should be confident that there is a sufficient clinical evidence to warrant prolonged, multidrug treatment regimens. In all situations, outcomes can be best optimized only when the clinicians, radiologists, and laboratories work cooperatively. The purpose of this article is to review the common presentations, diagnosis and treatment of the NTM that most commonly cause lung disease in Korea.