The phase equilibria of the La2O3-SrO-CaO-Mn3O4 system in air at 1200 degrees C has been studied. Under these conditions, eight univariant four-phase equilbria were observed. Quaternary phases, as well as liquid phases, were not observed. Perovskite-structure phases LaMnO3, SrMnO3, and CaMnO3 did not form complete solid solutions within the system.