Genomic DNA from nine individual bacteria, isolated from a diclofop-methyl-degrading biofilm consortium, was extracted for genetic characterization. The degradation of diclofop-methyl produces metabolites that are known intermediates or substrates for bacteria that degrade a variety of chlorinated aromatic compounds. Accordingly, oligonucleotide primers were designed from specific catabolic genes for chlorinated organic degradation pathways, and tested by PCR to determine if these genes are involved in diclofop-methyl degradation. DNA homology between the PCR products and the known catabolic genes investigated by Southern hybridization analysis and by sequencing, suggested that novel catabolic genes are functioning in the isolates. Specific fluorescent oligonucleotides were designed for two of the isolates, following 16S rDNA sequencing and identification of each of the isolates. These probes were successfully used for fluorescent in situ hybridization (FISH) studies of the two isolates in the biofilm consortium. Key words: consortium, catabolic gene, diclofop-methyl, 16S rDNA, FISH, SCLM.