Background: Since 1991 several outbreaks of acute coccidioidomycosis (CM) were diagnosed in the semi-arid Northeast of Brazil, mainly related to disturbance of armadillo burrows caused by hunters while digging them for the capture of these animals. This activity causes dust contaminated with arthroconidia of Coccidioides posadasii, which, once inhaled, cause the mycosis. We report on the identification of C. posadasii in soil samples related to outbreaks of CM. Results: Twenty four soil samples had their DNA extracted and subsequently submitted to a semi-nested PCR technique using specific primers. While only 6 (25%) soil samples were positive for C. posadasii by mice inoculation, all (100%) were positive by the molecular tool. Conclusion: This methodology represents a simple, sensitive and specific molecular technique to determine the environmental distribution of Coccidioides spp. in endemic areas, but cannot distinguish the species. Moreover, it may be useful to identify culture isolates. Key-words: 1. Coccidioidomycosis. 2. Coccidioides spp. 3. C. posadasii. 4. Semi-arid. 5. Semi-nested PCR. © 2011 de Macêdo et al; licensee BioMed Central Ltd.