The isothermal section at 600ºC of the phase diagram of the ternary system Hf-Ga-Sb was constructed in the whole concentration range, using X-ray powder diffraction. Limited solid solutions based on the binary compounds HfGa (17 at.% Sb), Hf 5 Ga 3 (11 at.% Sb), and Hf 5 Sb 3 (3 at.% Ga) were observed. Four ternary compounds form at 600ºC: Hf 2 GaSb 3 (structure type Zr 2 CuSb 3 , Pearson symbol tP6, space group P-4m2, a = 3.89841(8), c = 8.62650(19) Å), HfGa 0.1 Sb 0.9 (FeSi, cP8, P2 1 3, a = 5.5752(3) Å), Hf 5 GaSb 3 (Hf 5 CuSn 3 , hP18, P6 3 /mcm, a = 8.4747(5), c = 5.7190(5) Å), and Hf 5 Ga 1.84-0.72 Sb 1.16-2.28 (Nb 5 SiSn 2 , tI32, I4/mcm, a = 10.84972(15), c = 5.50154(8) Å for composition Hf 5 Ga 1.51(2) Sb 1.49(2)). The ternary phases, except HfGa 0.1 Sb 0.9 , are characterized by full or partial ordering of the Ga and Sb atoms.