Fission track (FT) ages were determined on 27 apatite and 21 zircon samples collected from three traverses across the eastern part of the Ryoke belt. FT zircon ages are reasonably consistent, averaging 58 Ma in the three traverses, suggesting uniform uplift and cooling of the region through the zircon isotherm (-240 ¿C). FT apatite ages range from 50 to 10 Ma and are divided into two groups: ''old'' apatites, located far from the Median Tectonic line (MTL), cluster around 54 Ma in the three traverses, also indicating uniform uplift and cooling through the apatite isotherm (-105¿C); and ''young'' apatites, located near the MTL, show age differences between the three traverses. FT length data of nine apatites reveal later thermal overprinting events near the MTL, probably due to shear heating induced by fault movements. The observed uplift and cooling rates of the Ryoke belt and the timing of motion along the MTL are discussed in the tectonic framework. ¿ American Geophysical Union 1988