The isothermal section at 500°C of the Sm–Ni–Al ternary system in the 40–100at.% Al region has been investigated by means of optical and electronic microscopy, quantitative microprobe microanalysis and X-ray powder diffraction. At this temperature six intermetallic phases have been determined. The existence of the Sm 4 Ni 6 Al 23 , SmNiAl 4 , SmNiAl 2 and SmNiAl phases, already known in the literature, was confirmed. Two new intermetallic phases and their crystal structures were determined, SmNiAl 3 , oP20-YNiAl 3 type and SmNi 2 Al 3 , hP18-HoNi 2.6 Ga 2.4 type.The phase relationships have been established and two ternary eutectic equilibria in the Al-rich region have been identified: E 1 , Ni-rich: Al+NiAl 3 +Sm 4 Ni 6 Al 23 and E 2 , Sm-rich: Al+SmAl 3 +Sm 4 Ni 6 Al 23 .