Objective:To isolate and identify Nocardiaspp. from soil in different regions of Isfahan province in the center of Iran.Methods:This study was conducted in 32 districts(16 cities and 16 villages)in Isfahan province during two years. A total of 800 soil samples from these regions were studied by using kanamycin. The isolated Nocardiaspecies were examined by gram and acid-fast staining and were identified biochemically and morphologically. The frequency and distribution of Nocardia spp. were determined in relation to different factors such as soil pH and temperate climate.Results:From 153(19.1%)Nocardiaisolates identified,Nocardia asteroids(N. asteroids)complex(45.5%) andNocardia brasiliensis(N. brasiliensis)(24.7%) were the most frequently isolated species, followed by Nocardia otitidiscaviarum (2.2%),Nocardiopsis dassonvillei,Actinom adura actinomadura(each 1.7%) and Nocardia transvalensis(1.1%) and also unknown spp.(23.0%). In this study, most species(54.4%) of Nocardia, especially N. asteroides complex were isolated fromsoils with pH: 7.01-8, whereas in pH: 8.01-9 more N. brasiliensis was isolated. The most Nocardia spp. was detected from regions with semi-nomadic and temperate climate(41.1%).Conclusions:N. asteroids complex is more prevalent in Isfahan province and soil can be a potential source of nocardiosis infections. It is to be considering that climate and soil pH are involved in the frequency and diversity of aerobic Actinomy cetes. Objective: To isolate and identify Nocardiaspp. From soil in different regions of Isfahan province in the center of Iran. Methods: This study was conducted in 32 districts (16 cities and 16 villages) in Isfahan province during two years. A total of 800 soil samples from these regions were studied by using kanamycin. The isolated Nocardiaspecies were examined by gram and acid-fast staining and were identified biochemically and morphologically. The frequency and distribution of Nocardia spp. were determined in relation to different factors such as soil pH and temperate Results: From 153 (19.1%) Nocardia isolates identified, Nocardia asteroids (N. asteroids) complex (45.5%) and Nocardia brasiliensis (24.7%) were the most frequently isolated species, followed by Nocardia otitidiscaviarum ), Nocardiopsis dassonvillei, Actinom adura actinomadura (each 1.7%) and Nocardia transvalensis (1.1%) and also unknown spp. (23.0%). In this study, the most species (54.4%) of Nocardia, especially N. asteroides complex were isolated fromsoils with pH: 7.01-8, while in pH: 8.01-9 more N. brasiliensis was isolated. The most Nocardia spp. was detected from regions with semi-nomadic and temperate climate (41.1%). Conclusions: N asteroids complex is more prevalent in Isfahan province and soil can be a potential source of nocardiosis infections. It is to be considering that climate and soil pH are involved in the frequency and diversity of aerobic Actinomyces.