Solid solutions of manganese-substituted brownmillerites and their stability range in the Ca2Fe2O5-"Ca2Mn2O5"-"Ca2Al2O5"-system were investigated. Samples were synthesized by solid-state reactions in temperature ranges at 1250 degrees-1300 degrees C. The phase development was investigated by powder X-ray diffraction and d-spacings and lattice parameters of new phases were determined. Ternary solid solutions of the hydraulic brownmillerites crystallize in a wide range of compositions (C2F-C(6)A(2)F-C(6)A(2)Mn-C(4)AMn-C(6)A(0.5)F(2)Mn(0.5)-C2F0.83Mn0.17). Brownmillerite, C(12)A(7) and C(3)A coexist at Al3+-additions above 66 mol%. Various oxygen defect perovskites are stable in the "C4FMn"-"C2Mn" field. "C2Mn" crystallizes as CaMnO2.8 and "C4FMn" as CaFe0.5Mn0.5O3-x. The other stability fields can be characterized by the coexistence of brownmillerite-type solid solutions and by different oxygen defect perovskites depending on the amounts of manganese and reaction conditions.