Bugs (Insecta: Heteroptera) are frequently used as examples of unusual cytogenetic characters, and the family Cimicidae is one of most interest in this respect. We have performed a cytogenetic study of the common bed bug Cimex lectularius Linnaeus, 1758 using both classical (Schiff-Giemsa and AgNO3-staining) and molecular cytogenetic techniques (base-specific DAPI/CMA3 fluorochromes and FISH with an 18S rDNA probe). Males originated from a wild population of C. lectularius were found to have 2n = 26 + X1X2Y, holokinetic chromosomes, 18S rRNA genes located on the X1 and Y chromosomes; achiasmate male meiosis of a collochore type; MI and MII plates nonradial and radial respectively.