The numbers of chromosomes of 106 species (62 genera) of Blattaria are given; the numbers for 84 species are reported for the first time. The numbers vary greatly in the suborder and range from n ♀ = 8 to n ♀ = 40. Differences in number occur also between species of a given genus. The most frequently occurring haploid number is 19. There is a trend toward higher chromosome numbers in the more recent and highly evolved Blaberidae (ovoviviparous and viviparous species). Submetacentric chromosomes are most commonly encountered, followed in frequency by metacentrics and acrocentrics.