A unique and scientifically most difficult aspect of predictive safety analysis of repositories for long lived wastes is the extrapolation of short term field and laboratory data to the long periods of time required by regulatory agencies for performance assessment. Natural analogues may be the only way of obtaining data on the cumulative effect of the migration of radionuclides over the time-scales of interest. This report briefly summarizes the state of the art in this field for technical specialists and may also serve as an introduction to the subject for managers. Contents: 1. Introduction; 2. Natural analogues in performance assessment; 3. Potential roles of analogues in performance assessments; 4. Analogues: Their applications and limitations; 5. Discussion of the quantitative and qualitative roles of analogues; 6. Conclusions and recommendations; Appendix A: Use of natural and archaeological analogues in performance assessment of the KBS-3 copper canister; Appendix B: The Cigar Lake uranium deposit: An analogue for nuclear fuel waste disposal; Appendix C: Uranium isotope studies combined with groundwater dating as a natural analogue.