The sequence specificity of the '10-23' RNA-cleaving DNA enzyme (deoxyribozyme) was utilised to discriminate between subtle differences in nucleic acid sequence in a relatively conserved segment of the L1 gene from a number of different human papilloma virus (HPV) genotypes. DNA enzymes specific for the different HPV types were found to cleave their respective target oligoribonucleotide substrates with high efficiency compared with their unmatched counterparts, which were usually not cleaved or cleaved with very low efficiency. This specificity was achieved despite the existence of only very small differences in the sequence of one binding arm. As an example of how this methodology may be applied to mutation analysis of tissue samples, type-specific deoxyribozyme cleavable substrates were generated by genomic PCR using a chimeric primer containing three bases of RNA. The RNA component enabled each amplicon to be cleavable in the presence of its matching deoxyribozyme. In this format, the specificity of deoxyribozyme cleavage is defined by Watson-Crick interactions between one substrate-binding domain (arm I) and the polymorphic sequence which is amplified during PCR. Deoxy-ribozyme-mediated cleavage of amplicons generated by this method was used to examine the HPV status of genomic DNA derived from Caski cells, which are known to be positive for HPV16. This method is applicable to many types of nucleic acid sequence variation, including single nucleotide polymorphisms.