This review describes how the application of molecular technology is providing improved methods for characterising and identifying taeniid cestodes. Emphasis has been placed on the use of DNA approaches for specific diagnosis of the various taeniid life-cycle stages, unambiguous species and strain discrimination, determination of evolutionary and phylogenetic relationships and the assignment of function to key macromolecules based on inferred amino acid sequences corresponding to cloned cDNA sequences. In addition, the review describes methods for isolating DNA from taeniids, approaches for cloning genomic and mitochondrial DNA from these organisms and the use of DNA methods for strain characterisation and egg detection. Lastly, the review focuses on the polymerase chain reaction (PCR) which can provide the basis for exquisitely sensitive assays diagnostic for individual taeniid species. Coupled with direct sequencing techniques, PCR can also provide a valuable new method for examining genetic variation between and within the various taeniid species.