The clinical observation, the work history, the analysis of pulmonary function tests and, mainly, the conventional x-ray chest radiograms have represented, til now, the diagnostic basis for pneumoconiosis (silicosis, mixed dust pneumoconiosis, asbestosis). Recently, the high resolution chest tomography (HRCT) has been introduced into the diagnostic procedures: such method seems to have its main application in the assessment of incipient clinical pictures of pneumoconiosis, particularly when characterized by normal pulmonary function tests. Asbestos fibers exposed workers were submitted to both radiologic methods. The great majority of them had already been recognized to be affected by asbestosis. A considerable statistical agreement (Cohen K) was observed between radiographic and tomographic I.L.O. classes. In conclusion, high resolution chest tomography doesn't appear to be an indispensable test for the diagnosis in admitted subjects, but we underline its importance in the evaluation of pleural thickenings.