Reporter strains of bacteria were tested using soil samples from several sites near a leaking fuel oil storage facility. The reporter bacteria utilized the bioluminescent lux genes from Vibrio fischeri, which were transcriptionally fused to catabolic gene sequences. The catabolic genes of interest specified the degradation of toluene (from the TOL plasmid) and naphthalene (from the NAH7 plasmid and from a NAH plasmid recently isolated). The results indicated that two soil samples were contaminated with both toluene (or xylene) and naphthalene. These data were useful in describing the extent of contamination at the site.