The following straight‐line relationship between the stacking‐fault probability &agr; and alloying concentration has been obtained by fitting published data:ln&agr;=ln&agr;0+K&agr; [C/(1+C)].In this expression,C=X/X*, whereXis the alloying concentration andX* is the solubility limit (both in atomic percent) at either the peritectic or the eutectic temperature, &agr;0is the stacking‐fault probability for pure silver andK&agr;is an experimental constant. The value of &agr;0, obtained by extrapolation, is 3.13±0.14×10−3;K&agr;is usually within the range 6.2±0.5, but is lower in those binary systems alloyed with the hcp elements Mg, Zn, and Cd. Similarly, an analytical expression relating stacking‐fault energy &ggr; and alloying concentration may be written asln&ggr;=ln&ggr;0+K&ggr; [C/(1+C)]2,where &ggr;0is the stacking‐fault energy of silver. The value ofK&ggr;for the Ag&sngbnd;Sn, Ag&sngbnd;In, and Ag&sngbnd;Al systems ranges from −10.0 to −10.5, but is −6.5 in the Ag&sngbnd;Zn system. The relationship between &agr; and &ggr; is discussed on the basis of these equations.