A Y-123 precursor has been obtained using the hydroxide co-precipitation method. The influences of the calcination time and temperature (with and without sintering and annealing) on the formation of the superconducting phase, YBa2Cu3O7-delta, are examined using XRD and T-c measurements. A comparison between the co-precipitated hydroxide precursor and the conventional dry precursor, obtained by mixing oxides acid carbonates, is made. It shows that thermal treatment of the hydroxide precursor at 750 degrees C already gives a superconductor, while the oxide-carbonate precursor is only superconducting after thermal treatment at 850 degrees C. (C) 1999 Elsevier Science Ltd. All rights reserved.