The family Retroviridae is composed of numerous non-icosahedral, enveloped viruses which possess two copies of a single-stranded RNA genome that has a short dimerized region. Retroviral genomes are non-segmented, of positive polarity, and typically between 7 to 12 kb long in size. All retroviral genomes consist of at least 4 genes, gag, pro, pol and env. The gag gene encodes the major structural polyprotein Gag and is all that is necessary and sufficient for the assembly non-infectious and immature viral-like particles. The viral protease is encoded by the pro gene and is responsible for facilitating the maturation of viral particles. Products of the pol gene include reverse transcriptase, RNase H and integrase while env is responsible for the viral surface glycoprotein and transmembrane proteins that mediate cellular receptor binding and membrane fusion. In addition, complex retroviruses such as HIV-1 encode accessory proteins that enhance replication and infectivity. Journal of Virology & Antiviral Research is an online journal that publishes stringently peer-reviewed, high-impact articles on basic retrovirus research.