A lead titanate (PbTiO3) precursor, prepared by the Pechini method, has been heat treated to study the transformation from amorphous to crystalline PbTiO3. Nucleation of PbTiO3 in the temperature interval 400 degrees-475 degrees C occurred before completion of the thermal decomposition of the polymeric precursor, resulting in nanocrystalline PbTiO3 with an unexpectedly high tetragonality (c/a ratio). Annealing and crystallite growth at 600 degrees C resulted in an increasing c/a ratio with annealing time in line with the expected finite size effect of PbTiO3. The unusually high c/a ratios observed in PbTiO3 nucleated at 400 degrees-475 degrees C are discussed in relation to partial reduction and point defects in PbTiO3.