Within the scope of a bilateral cooperation a series of Actiniae Migration Experiments were performed by FZK-INE at the Äspo Hard Rock Laboratory in Sweden. Several in-situ experiments investigating the migration of the actinides ²⁴¹Am, ²³⁷Np, ^242/244Pu, as well as of ²³³U and ⁹⁹Tc were performed in single fractured granite drill cores. These migration experiments were complemented by laboratory investigations. In all experiments, breakthrough of elements having relatively slow retention kinetics such as Np, Tc and U followed the tendency of the inert HTO tracer resulting in an initial breakthrough. Am and Pu was not found in the eluted water. The breakthrough behaviors could not be explained by a simple sorption mechanism. The redox sensitive actinides and Tc are reduced onto the surfaces of the natural fractures. In contrast, U(VI) remains stable and shows little sorption. Natural uranium present in the minerals of the granite was mobilized. The results of the in-situ experiments performed under conditions as close to nature as possible are summarized and some conclusions are drawn relevant for performance assessment.