AbstractGenetic variation within triatomine bugs was investigated by amplification of a 400 bp portion of the mitochondrial 16S ribosomal RNA gene by polymerase chain reaction (PCR), using evolutionarily conserved primers, from a selection of species representative of the genera Rhodnius, Triatoma and Panstrongylus. Amplification products were subsequently screened for sequence variation using single strand conformational polymorphism analysis (SSCP) and also subjected to direct sequencing. Single strand conformational polymorphism analysis could detect variation within and between genera; intraspecific variation was also detected and SSCP profiles appear to be useful for identification purposes at the inter- and intraspecific levels. A 290 bp multiple alignment of 15 sequences obtained from nine species was generated, phylogenetic inference subsequently used three methods; a distance estimate, maximum parsimony and maximum likelihood. This 16S region exhibited considerable variation which ranged from intergeneric to intraspecific levels. Phylogenies from these three methods of inference were in broad agreement. Triatoma and Panstrongylus were more closely related to each other than either was to Rhodnius, in keeping with the current taxonomic appraisal.