RESULTS: We combined a previously published implementation of a triplex DNA search algorithm with visualization to create a versatile R/Bioconductor package 'triplex'. The new package provides functions that can be used to search Bioconductor genomes and other DNA sequence data for occurrence of nucleotide patterns capable of forming intramolecular triplexes (H-DNA). Functions producing 2D and 3D diagrams of the identified triplexes allow instant visualization of the search results.