An apparatus is described which permits periodic inversion of the electric field during field inversion gel electrophoresis (FIGE) studies. The device is used in conjunction with a standard electrophoresis power supply and the gel electrophoresis cell. Adjustment of cycle period from 0.01 to 99.99 s and forward migration percent from 1% to 99% are accommodated either by local programming or from a personal computer via a RS‐232C interface.