An improved horizontal slab gel electrophoresis apparatus having compartments for vertical wicks at each end of a removable horizontal trough. Adjacent to the vertical wicks are vertical buffer compartments with built in electrodes. A partition separates the vertical wirks from the buffer compartment and includes a slot with a silicone plug which can be removed after curing or hardening of the vertical wicks to permit communication between the buffer and the gel slab. Flow adapters and an interconnecting tube permit constant circulation of the buffer to maintain equal volume and pH. The horizontal trough has slots for insertion of combs to form up to seventy-five sample wells and additional slots at each end for sealing the end of the horizontal slab when the gel slab is removed. The apparatus includes coils in a horizontal bed or plate beneath the trough for cooling the gel slab during a run and levelling screws for levelling the horizontal trough before pouring the gel slab.