Coccidioides immitis is the most virulent of the primary fungal pathogens of humans and other animals. As such, it is the only fungal aetiological agent designated as Biosafety Level 3 in Biosafety in Microbiological and Biomedical Laboratories, 3rd edn (Department of Health and Human Services 1993; http://www.nih.gov/od/ors/ds/pubs/bmbl/index.htm). Natural infection occurs via inhalation of aerosolized conidia from a primary environmental focus, and can also occur from traumatic implantation. In both instances, analogies can be drawn to Bacillus anthracis. Similarly, C. immitis was listed amongst the 'Select Agents' in the Final rule on Additional Requirements for Facilities Transferring or Receiving Select Agents in response to the US Antiterrorism and Effective Death Penalty Act of 1996, (Department of Health and Human Services 1996). Natural infection can resolve spontaneously following a primary pulmonary, flu-like episode, or can progress to a serious and life-threatening local or disseminated disease. Natural or experimental infection, appears to confer immunity, and efforts are underway to develop a protective vaccine. Such would be a welcomed addition to the limited antifungal armamentarium.