Apatite fission-track analyses from the area north of Jameson Land, East Greenland, indicate that the region has undergone at least three phases of cooling during the Mesozoic and Cenozoic. Two major periods of cooling during the Tertiary have been identified: a middle Tertiary episode, in which cooling began between 40 and 30 Ma, and a late Tertiary episode, in which cooling began between 10 and 5 Ma. The middle Tertiary event is synchronous with emplacement of major intrusive bodies associated with continental rifting and may be due either to uplift and erosion or hydrothermal effects. The late Tertiary event appears to be related to erosion associated with uplift resulting from changes in the North Atlantic spreading direction and associated events. No paleothermal effects have been identified related to the onset of rifting in the early Tertiary. Results from samples farthest from the continental margin reveal an earlier event in which cooling began between 225 and 165 Ma. The origin of this event is not clear, but it may reflect uplift and erosion associated with recognized unconformities within the Jurassic section.