Chromosome organization plays a key role in many biological processes. In viruses genome organization is essential for the packaging and releasing of the genome as well as for maintaining the stability of the viral capsid. This organization varies across different families and is highly dependent on the virus morphogenetic pathway (Casjens, 1997). In this review we will focus on the packing of double stranded DNA (dsDNA) in bacteriophages. Understanding how dsDNA is packed in bacteriophage capsids is important because it arguably yields the simplest example of a full genome organization in a biological system. Furthermore bacteriophages are believed to pack their DNA similarly to some animal viruses such as herpes and adeno-viruses (Casjens, 1997). Therefore understanding the basic principles of DNA packing in bacteriophages may provide essential insights into the viral assembly pathways for a wide range of bacterial and animal viruses. J. Arsuaga is supported by NIH grant 2S06GM52588–12. Peer Reviewed