Electrical conductivities of tetraethylammonium tetrafluoroborate in propylene carbonate were measured over wide ranges of salt concentration and temperature. The data have been interpreted in terms of ion-solvent and ion-ion interactions using the Lee-Wheaton equation at low concentrations and the semiempirical Castell-Arnis equation at high concentrations. The association constants, K(A), and limiting molar conductivities at infinite dilution, Lambda(0), have been calculated at (283.15, 291.15, 298.15, and 313.15) K. The results indicate that Et(4)NBF(4) is almost unassociated in this solvent medium. The evaluation of Stokes radii, r(S), of the ions at 298.15 K indicates that Et(4)N(+) and BF(4)(-) remain scarcely solvated in the propylene carbonate. The specific conductivity, chi, of Et(4)NBF(4) in propylene carbonate was determined in a concentration range of (0.15 to 1.4) mol.kg(-1) at (253.15, 273.15, 293.15, 313.15, and 333.15) K and was interpreted by the transition state theory. The activation energies for conductivity and for viscous flow are found to be not differing significantly meaning that the two transport processes are closely linked.