In the first half of 2005, we studied the emissions of off-road machines in Flanders and Belgium, for the environmental administration of the Flemish Government (AMINAL). This study was done in the context of the international emission inventories. It was performed in cooperation with the Dutch TNO-MEP. Until now, the emissions of off-road machines were one of the few types that were not assessed in detail yet. Because of increasing regulation levels and European emission inventory obligations, reliable emission assessments for this sector are required. Off-road machines produce an important amount of emissions: depending on the pollutant considered, their share is 5% to 20% of total road traffic emissions. The largest part of the off-road machine emissions, are produced in the agricultural, construction and industrial sectors. To produce these results, TNO built a new model combining the strong points of a number of existing models. The methodology consisted of a bottom-up calculation of the amount of work done by off-road machines.