We investigated the effect of uniaxial pressure (<$E 0~symbol Ш~1000> bars) applied parallely to the ac electric field on dielectric properties of PLZT-x/65/35 (<$E 2~symbol Г~x~symbol Г~13>) ceramics. There was revealed a significant effect of the external stress on these properties. The application of uniaxial pressure leads to the change of the peak intensity of the electric permittivity (<$E epsilon>), of the frequency dispersion as well as of the dielectric hysteresis. The peak intensity <$E epsilon> becomes diffused/sharpened and shifts to a higher/lower temperatures with increasing the pressure. It was concluded that the application of uniaxial pressure induces similar effects as increasing the Ti ion concentration in PZT system. We interpreted our results based on the domain switching processes under the action of combined electromechanical loading.