Recently, several chromosome banding techniques based on fluorescence in situ hybridization (FISH) have been developed for the human and the mouse genome. In contrast to the standard chromosome banding techniques presently used, giving a protein-related banding pattern, those FISH techniques are DNA-specific. Currently the FISH banding methods are still under development and no high resolution banding technique is available that can be used for a whole genome in one hybridization. Nevertheless, FISH banding methods were used successfully for research in evolution- and radiation-biology, as well as for studies on the nuclear architecture. Moreover, their suitability for diagnostic purposes has been proven in prenatal, postnatal and tumor cytogenetics, indicating that they are an important tool with the potential to partly replace the conventional banding techniques in future.