Changes in the composition of the soil mycoflora after soil treatment with 500, 2000 and 5000 ppm of mercury, zinc, lead, copper, nickel and cadmium, were determined on Czapek's glucose agar at intervals up to 15 weeks. Treatment of soil with mercuric chloride and lead nitrate significantly reduced the fungal population counts for soil treated with zinc or copper sulphate, and with nickel or cadmium chloride counts were increased on some treatments and reduced on others. When heavy metals were incorporated into the isolation medium, they depressed the total count of fungi, as well as affecting individual species.