Nontuberculous mycobacteria (NTM) are found widespread in nature. They can live in soil, water supplies, plants and various environmental conditions. Today there are nearly 100 known NTM species and more than 50 of them are associated with human diseases. NTM can cause pulmonary diseases, lymphadenitis, skin, soft tissue and skeletal infections, catheter related bloodstream infections and disseminated infections in patients with underlying diseases like AIDS, chronic obstructive pulmonary diseases, emphysema, bronchiectasis, cystic fibrosis and chronic alcoholism. The laboratory diagnosis of NTM has improved in parallel to the improvements in molecular biology. The new DNA sequencing and microarray technologies have been started to use in laboratories. Antibiotic susceptibility tests can be used both for taxonomic and clinical purposes. In this review article, the importance of laboratory diagnosis and antibiotic susceptibilities of NTM have been discussed.