The water-soluble phase of trinitrotoluene-containing sludge (SLP) was characterized with regard to trinitrotoluene (TNT) concentration, ecotoxicity, and a model biodegradation experiment as evaluation criteria for further development of appropriate treatment technologies. SLP contained 67.8 mg TNT/l. The results of germination and root-elongation tests indicated that SLP had a species-specific phytotoxic effect. The results of a 21 day degradation experiment demonstrated TNT conversion to 4-amino-2,6-DNT and 2-amino-4,6-DNT, with a simultaneous reduction in the total concentration of nitroaromatics. Addition of inoculum stimulated the TNT degradation process. The presence of the sludge solid phase inhibited microbial activity. Measurement of microbial enzyme activity was used to assess changes in the microbial community during the biodegradation process.