Traditionally, the retrovirus is regarded as an enemy to be overcome. Howev
er, for the past two decades retroviruses have been harnessed as vehicles f
or transferring genes into eukaryotic cells, a process known as transductio
n. During this time, the technology has moved from being a scientific labor
atory tool to a potential clinical molecular medicine to be used in gene th
erapy. This review explains the strategy for harnessing the retrovirus life
cycle, the scientific research and clinical applications of this methodolo
gy, and its limitations, as well as possible future developments.