The effect of pressure on the conductivity of fused zinc bromide and iodide was measured at pressures up to 1000 bar. At low pressures, the conductivity rises with pressure, and then, after a conductivity maximum, drops with a further increase in pressure. This is explained by the combination of two effects, a breakdown of the medium range structure into a more ionic structure with the increase in pressure (leading to an increase in conductivity) followed by a normal drop in conductivity with pressure, as is observed with ionic liquids. (C) 2012 Elsevier Ltd. All rights reserved.