The paper will focus on the valuation rules which were established at the start of the ROZ/IPD property index, the inprovement of the valuation rules afterwards and the reasons why ( ao quality control ). The paper will also show the differences between internal and external valuations, between dcf and income capitalisation valuations, as far as differences in frequency, discount rates, yields, rental growth etc are concerned and in what way these differences developed over time between 1995 and 2001. The last part of the paper will analyse the differences between the actual sale price and the latest valuation of transactions from 1995 through 2001.