Sub-solidus phase relations in the ternary CaO–La 2 O 3 –TiO 2 system at 1400°C in air were determined. The multi-phase samples were prepared by a solid-state reaction method, whereas the single-phase samples for the structure analysis of selected solid solutions were prepared by a wet-precipitation method in order to provide good homogeneity of the starting mixtures. The phases in the prepared samples were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS). The oxides form seven ternary compounds in the equilibrium state, many solid solutions (which extend across a broad concentration region), and a large, single-phase area based on the CaTiO 3 solid solution. The structures of several new phases – solid solutions on the tie lines CaTiO 3 –Ca 3 La 4 Ti 3 O 15 and La 2 TiO 5 –Ca 3 La 4 Ti 3 O 15 – were determined in detail.