The subfamily Triatominae, vectors of Chagas disease, represents one of the most cytogenetically studied subfamilies within the true bugs. To date, the chromosome numbers of more than 100 out of the 150 recognized species of the subfamily are known, resulting in an extremely stable group in terms of the number of autosomes (18, 20, and 22) and sex chromosome systems (mainly XY with variations in the number of X chromosomes). However, detailed analyses using laser flow cytometry, chromosome bandings, and FISH (ribosomal genes, X chromosome probes, genomic probes, and those from isolated repetitive fractions) have shown that this group is extremely diverse in their total genome content, as well as in the organization and types of sequences which constitute its chromosomes. In this chapter, we review and update current knowledge about the chromosome structure and highlight its importance to better understand the evolution of autosomes and sex chromosomes of this fascinating group of true bugs.