The temperature dependence of compressive strength of Ir 3 Zr, Ir 3 Hf, and Ir 3 Ti with an L1 2 structure was investigated. Ir 3 Zr showed weak anomalous behavior; in other words, the strength increased up to a peak strength with increasing temperature at intermediate temperatures but decreased slightly with increasing temperature below room temperature. Ir 3 Ti and Ir 3 Hf showed normal strength behavior. Their strength behavior including Ir 3 Nb is discussed in terms of the phase stability of the L1 2 structure with respect to other related structures. The lower phase stability of Ir 3 Ti with respect to the D0 2 4 phase suggests stable SISF-bounding dislocations, which cause the normal strength behavior to occur. The lower phase stability of Ir 3 Nb with respect to the D0 a causes anomalous behavior at intermediate temperature.