In 1977, a study had already been carried out on the decommissioning costs of NPP`s in Germany by NIS Ingenieurgesellschaft for the Commission of the European Communities. The experience gained during the last 15 years from the decommissioning of nuclear installations, as well as the developments made in calculating costs were the reasons to update the 1977 study. The cost estimates were carried out for the German LWRs, Biblis A (PWR) and Brunsbuttel (BWR). For the calculations, the software programme STILLKO 2 (owned by the German VDEW) was used. Besides cost calculations, data relating to manpower, occupational radiation exposure, masses of material to be dismantled and radioactive waste generated have been obtained. The results enable a direct comparison with those of the 1977 study and show the most important differences. In a separate chapter, costs for single items are presented in a way that comparison with decommissioning costs from other EC-countries may be possible.