The OECD standard Code for testing of agricultural and forestry tractors define rules enabling 30 official centres in 28 countries to produce comparable results. The first edition of the Codes dates from 1959 and, in the intervening 40 years, more than 1,700 tractors have been tested. Tractor tests carried out in accordance with the OECD Codes are given official approval provided that the Co-ordination Centre (CEMAGREF) certifies that the tests have been carried out in accordance with the procedures laid down in the Codes. This guarantee that the rules have been strictly applied ensures that the results obtained are fully comparable.Copublished with Cemagref.