The conductance of tetraisoamylammonium picrate at 30° in anisole (D = 4.28) over the concentration range 0.0001 < c < 0.01 has been measured at pressures from 1 atm to 5000 kg/cm2. The conductance at a given concentration decreases with increasing pressure in this range because the viscosity increases 11-fold. The product of equivalent conductance and relative viscosity, however, increases with increasing pressure. This effect is quantitatively accounted for by the increase of dielectric constant with pressure; with increasing dielectric constant, dissociation of ion pairs increases. The association constant is of the order of 109-1010. The minimum in the conductance curve is also shifted in the direction and by the amount calculated from the change in dielectric constant.