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Abstract Mycobacterium genus, including pathogenic and environmental species, is called non-tuberculosis mycobacteria. In this review, we assessed the research about the frequency of non-tuberculosis mycobacteria in Iran. The analyses showed that there are 16 and 28 mycobacterial species isolated in water and soil samples, respectively. The most frequent mycobacterial species in water were M. fortuitum (25.4%) and M. chelonae (25.4%), and in soil it was M. fortuitum (19.7%). The most frequent species in clinical samples was M. fortuitum, too. The frequency of non-tuberculosis mycobacteria in various clinical samples was various, and on average 1.1% of the suspected tuberculosis clients referred to the healthcare centers have non-tuberculosis mycobacteria. Keywords: Environmental Mycobacteria, Non-Tuberculous Mycobacteria, Iran, M. fortuitum