We grew leek (Allium porrum) in soils of two shooting ranges heavily contaminated with heavy metals in the towns of Zuchwil and Oberuzwil in Switzerland as a bioassay to test the activity of arbuscular mycorrhizal (AM) fungi in these soils. Soil samples were taken from (1) front of the shooting house (HOUSE), (2) the area between house and target (FIELD) and (3) the berm (BACKSTOP). Samples of Ribwort plantain (Plantago lanceolata) growing naturally within the shooting ranges were also collected and the colonization of its roots by mycorrhizal fungi was measured. The number of AM spores in the soils was significantly reduced concomitant with the increase in the degree of soil contamination with metals. In Zuchwil, mycorrhizal fungi equally colonized roots of Ribwort plantain sampled from BACKSTOP and HOUSE. In Oberuzwil, however, plants from BACKSTOP had lower colonization when compared with those sampled from HOUSE. Colonization of leek was strongly reduced in the BACKSTOP soil of Zuchwil and slightly reduced in the BACKSTOP soil of Oberuzwil when compared with plants grown in respective HOUSE soil. Concentrations of Cd, Cr, Cu, Ni, Pb and Zn in the leaves of leek grown in the BACKSTOP soil was within the range considered toxic for human consumption. This points to the high degree of bioavailability of these metal in these soils. Significant decrease in the number of mycorrhizal spores in the BACKSTOP soils in Zuchwil and the low colonization of leek roots grown in these soils point to possible changes in the species diversity of mycorrhizal fungi in these soils.