The Sm-In system was studied using differential thermal, metallographic and X-ray analyses. The following intermediate phases were observed: Sm 2In (melting point, 1090 ± 10 ° C), Sm 1+ x In (melting point, 1210 ± 20 ° C), Sm 3In 5 (melting point, 1110 ± 10 ° C) and SmIn 3 (melting point, 1130 ± 10 ° C). Five eutectics occur: β-Sm 2In (905 ± 5 ° C, 16.5 ± 1 at.% In), Sm 2In-Sm 1+ x In (1080 ± 10 ° C, 35 ± 0.5 at.% In), Sm 1+ x In-Sm 3In 5 (1090 ± 10 °C, 59.5 ±1 at.% In), Sm 3In 5-SmIn 3 (1075 ± 10 °C, 67 ± 1 at.% In) and SmIn 3-In (154 °C, more than 99.5 at.% In). β-Sm 2In decomposes eutectoidally at 800 ±10 °C and 12 ± 1 at.% In. The crystal structures of Sm 2In ( hP6, Ni 2In type), Sm 3In 5 ( oC32, Pu 3Pd 5-like type) and SmIn 3 ( cP4, AuCu 3 type) were confirmed. A structure of the cP2 CsCl type or the c12 tungsten type is suggested for the Sm 1+ x In compound. The general characteristics of the phase diagram are briefly discussed and compared with those of the La-In, Ce-In and Pr-In systems.