This study was intended to investigate the chromosome number, sex mechanisms and meiotic behavior of seven species of suborder Heteroptera collected from Bahir Dar at different localities by hand picking and insect net. Live adult male specimens were dissected under stereoscope microscope (B3040) in 0.67% saline solution and fixed in freshly prepared Carnoy’s fixative. The slides were stained with carbol fuchsin, mounted on a microscope and well spread stages were photographed. In the present study four species of Pentatomidae, two species of Coreidae and one species of Reduviidae were cytologenetically investigated. Out of the four Pentatomid species, a male diploid number of 14=12A+XY was found in Rhacognathus punctatus and Halyomorpha annulicornis while 16=14A+XY was observed in Podisus nigrispinus and Banasa dimidiata. Male diploid number of Coridae was found to be 18=14A+2m+X1X2O in Cletus borealis and 17=16A+XO in Acanthocephala femorata, while male diploid number of Reduviidae was 22= 20A+XY in Androcluspictus. Microchromosomes were present in one species of Coreidae (Cletus borealis) and absent in the second species of Coreidae, all Pentatomidae and Reduviidae of this study. Cytogenetic observation of all the seven species is the first in Ethiopia and those of Rhacognathus punctatus (Pentatomidae) and Acanthocephalafemorata (Coreidae) was the first for the cytogenetic world. Certain characteristics are common in the three species of Heteroptera such as fusion of the X and Y to form a heteropycnotic body at diffuse stage, and their behaviour at diakinesis and metaphase II. Sex chromosomes, X1 and X2, remain fused throughout meiosis in Cletus borealis. Key words: Heteroptera, Pentatomidae, Meiosis, chromosomes