The recent publication by the World Bank of PPP-GDP estimates for 2005, referred to 146 countries, seems a good occasion to reopen the long-standing debate on the use of Purchasing Power Parities. While theoretical speculations on the subject have continued, no estimates were supplied for more than a decade. The author’s alternative method for GDP estimation is based on inflationadjusted long-term exchange rates, where real GDP estimates are obtained through simultaneous equations. He describes the method in the light of his experience and compares its results for 100 countries with both ICP estimates and GDPs at exchange rates.