Phase relations were determined in the Ag–Sb system through the temperature range 500° to 300 °C to permit a better understanding of the origin of certain silver ores and to provide a base for the study of more complex sulfosalt systems. The Sb-rich solvus for the ε phase (Ag6 ± xSb) at 500°, 450°, 350°, and 300 °C occurs at 18.2, 17.75, 17.75, and 17.7 weight percent Sb, respectively. The Ag-rich solvus of the ε′ phase (dyscrasite) occurs at 22.5% Sb at 500 °C and 22.9% at 450°, 400°, 350°, and 300 °C. The Sb-rich solvus of this phase occurs at 27.2% Sb at 500°, 450°, 400°, and 350 °C. Therefore the atomic silver to antimony ratio ranges from nearly 4 to 3, and the formula may be written Ag7 ± xSb2. An order–disorder transition of ε′ to a third phase, ε″, reported to occur at about 440° to 449 °C, was not observed. The compositions of the solid solutions relate to high angle X-ray powder reflections through the following functions: for ε phase, d = 0.000150x + 0.79743, and for ε′ phase, d = 0.00160x + 0.76608, where d is the specific interplanar spacing in Ångstroms and x is the weight percent antimony.