The purpose of this study is to develop a methodology to predict the low-cycle (large strain—from 0.1 to 0.35 strain) fatigue life of solders subject to thermal cycling. Solders are commonly used in electronic assemblies. Using thermal fatigue data measured for 80In15Pb5Ag, a low-cycle fatigue curve for 80In15Pb5Ag solder subject to thermal cycling was developed. Specifically a Coffin-Manson relationship was derived for the solder, with a high degree of correlation (see Table I), for four different failure criteria, defined in the body of the paper. This relationship, together with calculated strains in the solder joint, allows the low-cycle fatigue life of the solder joint to be predicted.