A phase diagram of the system CaF2-GdF3 was studied by thermal and X-ray analysis. Two wide domains of solid solutions based on CaF2 and a high-temperature modification of α-GdF3 (LaF3-structural type) are present in this system. Two maxima were found on the melting curves of the Ca1−xGdxF2+x and α-(Gd1−yCayF3−y solid solutions, at 1428 ± 10‡ (5 mole % GdF3) and 1282 ± 5‡ (85 mole % GdF3), respectively. The coordinates of the eutectic are 60 mole % GdF3 and 1233 ± 5‡.