The objective of this study is to determine the influence of partial substitutions of Zr by Hf in the perovskitetype crystalline structure of PbZrO(3). Different samples over the whole composition range (0 < or = x < or = 1) in the PbZr(x)Hf(1-x)O(3) family have been prepared. Phase transitions have been determined by thermal analysis (DSC) and complex impedance (IS) spectroscopy over a wide temperature range. As a consequence of the cation replacement, the changes that take place in the different phase transitions temperatures are reported. By both techniques, thermal analysis and electrical characterization, it is shown that for all compositions prepared there are 2 phase transitions in a temperature range between 160 and 230 degrees C. With these results and the previously known crystalline structure of pure PbZrO(3) and PbHfO(3) perovskites, the phase diagram of the PbZr(x)Hf(1-x) O(3) family is presented for the first time.