The technique of using whole mounts to study chromosomes and early cleavage in insect eggs was first developed by Schmuck and Metz (1931) ; subsequently, the technique was modified by Whiting (1950) and von Borstel and Lindsley (1958). The Schmuck-Metz method largely eliminates tedious embedding in paraffin and sectioning of eggs. However, we encountered difficulties when we attempted to use the technique or its modifications to study radiation- or chemosterilant-induced chromosomal abnormalities in house flies, Musca domestica L. We could not achieve the necessary reproducibility of staining or process large numbers of eggs without causing chromosomal distortion. Therefore, the method described here of obtaining acceptable whole-mount preparations for the study of chromosomal aberrations was developed.