An assay that makes use of differences in thermal stability between perfectly and imperfectly matched hybrids in combination with a sensitive chemiluminescence detection system was developed and applied to the identification of CYP1A1 polymorphisms. In this assay, two oligonucleotide probes for each polymorphic site were designed: one perfectly matching the wild type allele, the other perfectly matching the mutant allele. The genotypes were determined by calculating the ratio of signals obtained from the two probes. The method described here allows for the rapid, simple and cost-effective detection of DNA polymorphisms. Compared with fluorescence- and microarray-based assays, this method provides an alternative for genotyping where costly equipment or specialized reagents are not available.