Effects of uniaxial stress on the dielectric properties of ceramics in lead magnesium niobate-lead zirconate titanate (PMN-PZT) system are investigated. The ceramics with a formula (x)Pb(Mg1/3Nb2/3)O3-(1 - x)Pb(Zr0.52Ti0.48)O3 or (x)PMN-(1 - x)PZT when x = 0.0, 0.1, 0.3, 0.5, 0.7, 0.9, and 1.0 are prepared by a conventional mixed-oxide method. Phase formation behaviour and microstructural features of these ceramics are studied by x-ray diffraction and scanning electron microscopy methods, respectively. The dielectric properties under the uniaxial stress of the PMN-PZT ceramics are observed at stress levels up to 5 MPa using a uniaxial compressometer. It is found that with increasing applied stress the dielectric constant of the PZT-rich compositions increases slightly, while that of the PMN-rich compositions decreases. On the other hand, the dielectric loss tangent for most of the compositions first rises and then drops with increasing applied stress.