Existing dams have been evaluated according to the current knowledge at the time of their construction. But these evaluations do not satisfy the current safety needs. In practice, for new dams the procedures recommended by ICOLD are applied. The general procedure is clear and straightforward. But often detailed procedures and criteria are needed. Practice has shown that the assessment of the earthquake loading function leads to extensive discussions with the designers. Experiences with deterministic and probabilistic methods are discussed in respect to data acquisition, evaluation of data and reliability of results.