Phage DNA packaging occurs by DNA translocation into a preformed protein shell--a prohead--with the aid of a packaging enzyme or a terminase. The packaging enzyme is composed of two subunits: the large subunit has ATP-binding, prohead binding, and DNA cleavage activities, and the small subunit is a DNA binding protein. DNA translocation is driven by ATP hydrolysis. In general, phage DNA replication mechanisms lead to the accumulation of concatemers. Concatemers are processed to mature DNA during and depending upon DNA packaging. This review will focus on the molecular mechanism of concatemer processing and the coupling of ATP hydrolysis to DNA translocation.