  The effect of pressure on the low-frequency dielectric constant,
$\epsilon_0$, of single crystals of KNbO_3 is investigated by means of
capacitance measurements. The dielectric constant increases with pressure up to
22.5 kbar, where it exhibits a large value ($\epsilon_0$ = 5000), and then
decreases. This change in its behaviour is related to a phase transition
induced by pressure. On decompression, the samples do not revert back to the
ambient pressure phase.
