The dielectric and piezoelectric properties of the (Pb0.985Bi0.01)(Ni1/4Zn1/12Nb2/3)(x)(ZrsigmaTi1-sigma)(1-x)O-3 piezoelectric ceramic system (0.2 less than or equal to x less than or equal to 0.7, 0.1 less than or equal to sigma less than or equal to 0.9) were systematically investigated. The results showed that, after poling, the dielectric constant, epsilon(33)(T), increased for the tetragonal compositions but decreased for the rhombohedral compositions. Furthermore, high values of epsilon(33)(T) and piezoelectric modulus, d(31) were found for the compositions along the extension of the morphotropic phase boundary. The highest values of the planar electromechanical coupling factor, K-p, and the piezoelectric modulus, d(31), were found to be 0.70 and -274 x 10(-12) C N-1, respectively. The Curie temperature, remanent polarization, coercive field and the lattice constants of the a and c axes in relation to the Pb(Ni1/3Nb2/3)O-3 content and the Zr/Zr + Ti ratio were also determined.