Undoped CaCu3Ti4O12 and cobalt doped CaCu3Ti4-xCoxO12 (CCTCO) with x=0.10, 0.20 and 0.30 were prepared by semi-wet route for the first time using solid TiO2 powder and metal nitrate solutions. XRD analysis confirmed the formation of single-phase material in the samples sintered at 900 degrees C for 6 h. Structure does not change on doping with cobalt and it remains cubic in all the three compositions studied. Lattice parameter increases slightly with cobalt doping. SEM micrographs of the CaCu3Ti4-xCoxO12 samples show that the grain size is in the range of 2-8 mu m for these samples. EDX studies show the percentage of elements along with the grain and grain boundary, which confirm the rich phase of copper oxide at grain boundaries. Dielectric properties have been measured as a function of temperature and frequency. (C) 2010 Elsevier B.V. All rights reserved.