Abstract: Apparatus and method for conducting electrophoresis in a capillary tube under the influence of a pulsed electric field. Apparatus for separating and detecting molecular species of a sample in a conductive medium includes a capillary tube for containing conductive medium, means for introducing a sample into a conductive medium-filled capillary tube, means for applying a pulsed electric field across the conductive medium-filled capillary tube between its ends, and means for detecting constituent molecular species of a sample in a conductive medium-filled capillary tube as they traverse the tube. A method for separating and detecting molecular species of a sample in a conductive medium includes the steps of introducing the sample into a capillary tube filled with conductive medium, applying a pulsed electric field of up to 500 volts/centimeter between the ends of the capillary, and detecting the constituent molecular species of the sample as they traverse the capillary.