Life threatening infection with species of the Burkholderia cepacia complex frequently occurs as a result of cross infection among individuals with cystic fibrosis. Stringent infection control measures have decreased but not eliminated such infection in this vulnerable population, implying that non-patient reservoirs contribute to ongoing acquisition. However, strains common to both the natural environment and patients with cystic fibrosis have not yet been described. By use of various genotyping methods, we have identified from agricultural soil the B cepacia genomovar III strain that is most frequently recovered from cystic fibrosis patients in the mid-Atlantic region of the USA. This finding indicates that human pathogenic strains are not necessarily distinct from environmental strains, and might help explain ongoing human acquisition despite strict infection control measures.