In all European Union countries the classification of economic activities that is used in the Business Surveys is currently rebased from NACE Rev 1.1 to NACE Rev. 2. This paper describes some of the methodological problems encountered with the changeover to the NACE Rev. 2. Different sampling and estimation strategies are proposed to produce reliable figures for the domains under both classifications simultaneously. Furthermore several methods are described that can be used to reconstruct time series for the domains under the NACE Rev. 2.