Structural properties and the influence of d electrons' insertion in PbTiO3 have been determined in the study of PbM1-x'O-3 (M, M' = Ti, Cr, and V) solid solutions by means of X-ray diffraction, high-resolution transmission electron microscopy, magnetization measurements, and strain mapping analysis. PbTi1-xVxO3 is the only system that preserves the same space group (P4mm) for all x, whereas PbTi1-xCrxO3 and PbV1-xCrxO3 change to cubic (Pm (3) over barm) at x = 0.30 and 0.4, respectively. These values have been related with the percolation threshold for a cubic net (P-c = 0.31). The microscopy study coincides with the X-ray diffraction determination, and neither supercell nor short-range order maxima are observed. However, for x >= 0.7 in PbTi1-xCrxO3 the presence of modulated zones is observed in both the electron diffraction pattern as well as high-resolution transmission electron micrographs, as is typical for PbCrO3.(1) Furthermore, the tetragonal region in PbV1-xCrxO3 suffers a great stress because of the contrast of [Cr-O-6] octahedra and [V-O-5] square-based pyramids end members basic units.