Bacteria from polluted and agricultural soils antagonize the growth of Phanerochaete chrysosporium on solid media. The antagonistic bacteria in a soil contaminated with trinitrotoluene included fluorescent pseudomonads. Antagonism by fluorescent pseudomonads was variable according to the pH, and carbon and nitrogen sources used in the growth medium. A fluorescent siderophore produced by a Pseudomonas putida strain did not inhibit the growth of Phanerochaete chrysosporium but pseudomonad isolates capable of producing phenazine derivatives were strongly inhibitory.