Rhenium-osmium (Re-Os) geochronology of molybdenite provides a tool to directly date mineralizing events in hydrothermal systems. In the Yukon-Tanana upland of eastern Alaska, numerous molybdenite-bearing porphyry occurrences are recognized. The deposits are related to middle and Late Cretaceous granitoids (Kreiner and others, 2019; 2020). Some of the porphyry districts have multiple superimposed igneous events with relative timing relationships observed through detailed mapping and core logging. These timing relationships indicate multiple pulses of copper and molybdenite mineralization. This study dated molybdenite-bearing veins from porphyry occurrences across eastern Alaska. This includes five samples from the Taurus district, which attempted to directly date mineralization in an effort to understand which of the seven magmatic pulses was the main cause of mineralization.