[en] In Belgium recent national and community legislation regulates emission levels of 'acid pollutants' (SO₂, NO_x) and apply to large combustion facilities whose pollutants are transported over large distances. Complying with this legislation requires costly emission control equipment. In order to minimize the costs of clean-up operations, this paper analyses the potentialities of an emission trading programme by means of a linear programming model. Six retrofit power plants have been chosen to test the model. As the results suggest, substantial credits are obtained for either SO₂ or NO_x emissions reduction. 13 refs., 2 figs., 5 tabs