Epidemiological surveys of coal workers' pneumoconiosis are only possible by means of periodic X-ray examinations, repeated with a reasonable frequency in order to allow an identification of the first X-ray anomalies of simple pneumoconiosis in exposed workmen. Incidence studies to detect simple pneumoconiosis at its first stages and its progressive increase in cohorts of coal-miners whose dust exposure is known are indeed theoretically the best way to approach these problems. For many reasons, discussed in this paper, such incidence studies are nowadays impossible in Belgium. The survey technique used in our country is based on repeated transversal surveys. Its results are illustrated and commented.