Real-time transmission electron microscopy (TEM) was used to directly examine the temperature dependence of electromigration-induced void and failure dynamics over the range 200–350 °C. The studies were done using submicron Al interconnects and a special sample stage, which allowed TEM observations to be recorded while heating and passing current through the sample. A novel sample design dramatically minimized any Joule heating in the runners. Our experiments directly reveal that the mechanism responsible for void and failure dynamics at temperatures <250 °C is distinctly different from that at higher temperatures. These results have implications regarding methods used for predicting electromigration reliability at use conditions from accelerated test data. ©1998 American Institute of Physics.