The ability of seven different isolates of wood-rotting fungi to decolorize a wide range of structurally different synthetic dyes was investigated. All isolates decolorized some dyes, and all dyes were decolorized to some extent. Color removal efficiency varied from 100% to only ca. 50% at most for chrysophenine. Some decolorizations were extremely rapid. Two isolates reduced the A(625) of a solution of brilliant green from 57 to 0.5 in 1 day. No one isolate proved to be best for all dyes, and same were poor in most tests. Phanerochaete chrysosporium was among the least effective of the isolates. The screening system, which was unoptimized, employed mycelial mats pregrown on malt extract medium and supplied with an energy source, glucose, together with the dye.