Abstract: A pulsed field electrophoresis method and apparatus for the separation of molecules wherein a fixed polarity potential difference between an anode and a cathode, disposed at respective opposed edges of the gel, produces a fixed polarity electric field in the plane of the gel; and simultaneously, a second set of electrodes, disposed on each side of the gel, and between which an alternating polarity potential difference is applied, produce an alternating polarity electric field orthogonal to the plane of gel. The combination of the fixed polarity and alternating electric polarity fields give unprecedented resolution in the separation of molecules across a wide range of molecular sizes.