The phase diagram of the quasi binary NaBr-DyBr3 system was determined by differential thermal analysis (DTA) applied to 27 samples covering the complete composition range of the system. The 3NaBr*DyBr3(s) compound is present in the solid-phase in addition to the pure component halides NaBr(s) and DyBr3(s). The DyBr3(s) and 3NaBr*DyBr3(s) phases showed a polymorphic transition at 1112 and at 733 K, respectively. The {DyBr3(s) + 3NaBr*DyBr3(s)} eutectic mixture melts at 709 K giving a liquid of the molar composition x(NaBr) = 0.62. The 3NaBr*DyBr3(s) phase melts peritectically at 765 K. The phase diagram obtained in the present study virtually agrees with the calculated one available in literature. (c) 2004 Elsevier B.V. All rights reserved.