So far 371 species and subspecies of 20 families of the three living suborders have been studied cylologically. this figure represents more than 6% of the total number of species described, making dragonflies cylologically by far the best studied order of insects, A review is given of the main data on the chromosomal cytology, viz. haploid chromosome number, general morphology and origin of the karyotype, distinctions, if any, between geographic populations, peculiarities in chromosome behaviour and mode of sex determination of all species and subspecies hitherto studied. In addition, a complete bibliography related to the subject is presented.