Polycrystalline samples of Bi 2 W 1− x Me x O 6− y (Me=Nb, Ta) solid solutions have been prepared by solid-state reactions, and the influence of Nb and Ta substitutions for W on the polymorphism and electrical properties of Bi 2 WO 6 has been studied. The limit of the solid solutions is at x=0.1 for Me=Nb and at x=0.15 for Me=Ta. The distinctive features of the polymorphism of the Nb- and Ta-doped materials have been identified. According to differential scanning calorimetry data, tantalum and niobium substitutions for tungsten increase the temperature of the high-temperature, orthorhombic-to-monoclinic reconstructive phase transition and suppress the transition starting at x=0.05 for Me=Nb and x=0.10 for Me=Ta. As a result, the Bi 2 W 1− x Nb x O 6− y samples have an orthorhombic Aurivillius-type structure up to their melting point. The Bi 2 W 1− x Ta x O 6− y solid solutions at high temperatures consist of a mixture of an orthorhombic and a monoclinic phase. Nb and Ta doping shifts the ferroelectric phase transition to lower temperatures by more than 200°C, thus markedly extending the stability range of the nonpolar orthorhombic paraelectric phase, which exists in a temperature range as narrow as 930–960°C in the case of undoped Bi 2 WO 6 . The increase in oxygen vacancy concentration due to heterovalent substitutions of Nb 5+ and Ta 5+ for W 6+ leads to an increase in conductivity by two orders of magnitude relative to the unsubstituted compound.