Different tectonostratigraphic units of the Hardangervidda-Ryfylke Nappe System have been dated by Rb/Sr methods. The three lowest units of the allochthon gave the following results, recorded from below: The HolmasjØ Formation, 409 ± 15 m.y.; the Dyrskard Group, 1289 ± 80 m.y.; the Kvitenut Complex, 1643 ± 88 m.y. The highest part of the allochthon, the micagneisses of the Revsegg Formation, yielded a quite ambiguous result, 430 ± 250 m.y., indicating a Caledonian metamorphic influence on Paleozoic and/ or Precambrian material. An age of 943 ± 100 was obtained on the supracrustal series of the basement in Valldalen.