To study the signs of coal worker's pneumoconiosis (CWP) at computed tomography (CT), the authors obtained thoracic CT scans in 170 coal-dust-exposed workers who were concomitantly evaluated with conventional posteroanterior and lateral radiography. The profusion and extent of disease was assessed by means of CT in two groups of miners: group 1 (n = 86), miners with worker's compensation and radiographic evidence of CWP, and group 2(n = 84), miners who had applied for compensation without radiographic evidence of CWP. The CT signs of CWP consisted of micronodules, nodules, and progressive massive fibrosis. The comparative analysis demonstrates the superiority of an optimal CT technique over chest radiography in the evaluation of simple silicosis, with improved sensitivity in the detection of small parenchymal opacities. CT provides additional information on the stage of the disease but also clarifies some ambiguities of the ILO classification of small opacities. CT was equivalent to radiography for complicated silicosis, except in the identification of necrosis. CT evaluations are complementary to plain radiography in the assessment of CWP, and the addition of high-resolution CT is useful in achieving a more accurate evaluation of the small parenchymal opacities.