Abstract: Electrophoresis apparatus having a housing, a substantially horizontal cooling bed within the housing for supporting and cooling a medium during electrophoresis, a transparent cover overlying the bed, and first and second electrode troughs along opposed sides of the bed. A condenser coil has an open central area greater than the area of the bed and overlies the bed with the open area located above a vertical projection of the bed. Major segments of the condenser coil overlie the electrode troughs. The condenser coil and the cooling bed are arranged for serial fluid flow with coolant fluid introduced into the condenser coil and withdrawn from the cooling bed. The cooling bed itself has first and second generally parallel plates spaced apart by a core which defines a tortuous path for fluid flow. One of the plates has a higher thermal conductivity than the other. By inverting the cooling bed, differing cooling rates can be achieved.