At atmospheric pressure, alloys of high‐pressure InSbIIand &bgr; Sn are retained indefinitely as metastable phases at 77°K but are transformed into stable two‐phase mixtures of low‐pressure InSbIand Sn at sufficiently high temperatures. The resistivity of these alloys at 77°K has been measured as a function of composition, and the temperature and time dependence of resistivity up to 300°K has been determined for samples containing up to 60 at.% Sn. The data show that at any temperature the rate of transformation decreases monotonically with increasing Sn content, and, therefore, that solid solutions of InSbIIand Sn are formed up to at least 60 at.% Sn. The data are thus consistent with complete solid solution in the InSbII&sngbnd;Sn system, as previously concluded on the basis of superconductivity data.