The results of > 20 yr of geochronological studies in the Yukon crystalline terrain of east-central Alaska and W Yukon Territory suggest at least six igneous and thermal (metamorphic?) events. Plutonism during Mississippian, early Jurassic, mid-Cretaceous, late Cretaceous and early Tertiary times is indicated. Evidence also indicates that Mississippian, early Jurassic, late early-Cretaceous, and late Cretaceous thermal (metamorphic?) events have affected parts of the terrain. The western part was affected by a significant regional metamorphic event in late early-Cretaceous time, followed by a terrain-wide mid-Cretaceous plutonic event. The pattern of K/Ar ages allows division of the terrain into domains, bounded by NE-trending lineaments. The K/Ar ages (204) are tabulated, with K/Ar ages of 10 mineral pairs.-P.Br.