Tight certification standards for new motor vehicles have always been the basestock for legislative efforts to control motor vehicle related air pollution. However, new additives need to be used when composing the formula for today's situation, where the relative contribution of new vehicles to the overall emissions is quickly diminishing and in-use performance is starting to play an increasingly important role.This paper outlines the general lay-out of the Finnish in-use control programme, which was started January 1, 1993. The choice of test procedure as well its initial verification are discussed. Determination and validation of the cut-points is also closely detailed. The main emphasis of the paper, however, lies in the practical experience gathered during the three-year planning and field testing phase that preceeded the introduction of the programme. Items that are typical for Finland, like cold ambient conditions, are more deeply discussed. Furthermore, some data from the results collected during the first 7 months of the programme is presented.Motor vehicles account a major share from many air polluting gaseous emissions. In addition, diesel powered vehicles emit fine particulates, which can have detrimental effects both on the environment as well as human health. Hence, many countries have introduced legislative efforts to control these emissions. Traditionally, these measures have mainly been targeted towards new vehicles, which have to be type approved according to relevant rules and regulations before they can enter the market.The progressive lowering of the standards world-wide has spurred the industry continuously to develop emission control technology. Mainly due to the widespread use of three-way-catalyst systems, the emission level of a new automobile has lowered so much, that its contribution to the overall emissions of the whole vehicle park is beginning to be almost neglible. Therefore, the lowering of standards for a new vehicle has lost most of its power to control total emissions. The performance of in-use vehicles has become overruling instead. Thus further reduction in emissions cannot be achieved without actions focused to in-use vehicles, as well.