In this paper, we report the synthesis, structure and electrical properties of the perovskite-type AZn(0.33+x)Nb(0.67-x)O(3-delta) (A = Sr or Ba; 0 <= x <= 0.08). The investigated compounds were prepared by employing the solid-state (ceramic) reaction using alkaline nitrates, zinc oxide, and niobium oxide at elevated temperatures in air. Powder X-ray diffraction (PXRD) showed the formation of disordered Zn and Nb at the B-sites of space group Pm (3) over barm with cubic structure and a lattice constant comparable to that of the literature. The AC impedance study showed mainly bulk contribution to the total electrical conductivity over the investigated frequency range of 0.01 Hz to 1 MHz in all the investigated atmospheres even at low temperatures, which is significantly different from that of the well-known perovskite-type B-site ordered BaCa0.33+xNb0.67-xO3-delta) and the disordered acceptor-doped BaCeO3. The bulk dielectric constant determined at 500 and 700 degrees C in air was found to be in the range of 35-100. In air, the isothermal bulk dielectric constant seems to increase with an increasing Zn content, and a similar trend was observed for total electrical conductivity. In dry and wet H-2, the electrical conductivity decreases with an increasing Zn content in AZn(0.33+x)Nb(0.67-x)O(3-delta), and the x = 0 member of the Ba compound exhibits the highest total conductivity of 7.2 x 10(-3) S cm(-1) in dry H-2 at 800 degrees C. Both Sr and Ba compounds were found to be stable against the reaction with pure CO2 at 700 degrees C and H2O at 100 degrees C for a long period of time. SrZn0.33+xNb0.67-xO3-delta was found to be stable in 30 ppm H2S at 800 degrees C, while the corresponding Ba compound formed reaction products such as BaS (JCPDS Card 01-0757), BaS2 (JCPDS Card 21-0087), and BaS3 (JCPDS Card 03-0824).