The dielectric properties and conductivity of the (C3H5N2)(5)Bi2Cl11 crystals (abbreviated as ICB) in the paraelectric-ferroelastic phase have been studied by impedance spectroscopy as a function of temperature. The low frequency anomaly of the electric capacitance observed in ICB crystal has been found to be qualitatively similar to that observed at the superionic phase transitions in some protonic conductors. The (C3H5N2)(5)Bi2Cl11 crystals have been shown to be characterized by considerably high (10(-2) S/cm) conductivity above 293 K. The nature of this conductivity seems to be based on a Grotthuss mechanism of proton transport. (C) 2007 Elsevier B.V. All rights reserved.