In this paper we present the first data on a single crystal of Gadolinia doped Ceria (CGO). The crystal was prepared using inductive melting in a cold crucible. The cell parameter (a = 5.426 Angstrom) was estimated using XRD on a powdered sample. The conductivity was measured by impedance spectroscopy in N-2, O-2 and air between 190 and 550 degrees C. The activation energy was found to be 1.1 eV. The diffusion and surface exchange coefficients were determined using O-18 isotope exchange and SIMS. The activation energy for the diffusion process was found to be 1.16 eV. A transition in the activation energy of the surface exchange coefficient from low to high was seen at around 650 degrees C.