BaTiO3 ceramics containing Mn acceptors and various Mo, W and Nb donor dopants have been fired in reducing atmosphere and re-oxidized in N2/O2. In single Mn-doped ceramics, Mn2+ is completely oxidized to Mn3−; in N2 containing 50 ppm O2 at T > 800°C. Changes of the Curie point and sample length under reduction and re-oxidation have been detected using dielectric and thermomechanical measurements. Charge compensation and complex formation between acceptors and donors have been observed. In donor-acceptor charge complexes, Mn2+ cannot be oxidized.