The complete mitochondrial genome of the bristletail Petrobius brevistylis has been determined. The genome is 15 698 bp long and bears the standard set of genes common to all arthropods as well as a major non-coding A + T-rich region, the putative mitochondrial control region. A unique gene order was revealed as it differs from other hexapod and crustacean mitochondrial genomes in the position of tRNA-Tyr. Genome features like nucleotide composition and codon usage are compared with that of other insect taxa. A + T content is similar in species of Archaeognatha and Zygentoma, but obviously lower than in Collembola and Pterygota. This A + T bias significantly affects also amino acid frequencies and may be a problem for phylogenetic analyses.