The present invention provides a process for the production of a closed linear DNA comprising the steps of (a) providing a DNA template comprising a DNA sequence of interest; (b) amplifying DNA from the DNA template of step (a) wherein the amplification is primed with a primase/polymerase enzyme; (c) generating a closed linear DNA with the amplified DNA produced in step (b); and (d) purifying the closed linear DNA produced in step (c). The invention also provides a closed linear DNA obtainable according to the process of the invention, a pharmaceutical composition comprising a therapeutically effective amount of the closed linear DNA of the invention, and a concatameric DNA comprising repeats of a DNA sequence of interest.