The morphology of pneumoconiosis occurring in dental technicians could be studied by systematic light and electron microscopical investigation of 30 lung preparations from such cases. Diffuse streaky fibrosis and, in some cases, nodular fibrosis was observed together with occasional formation of silicotic nodules that may lead to extensive transformation of the alveolar structure. The etiological relationship between occupational dust exposure and pulmonary changes could be documented by element analysis of dust deposits on histologic sections, and of dusts from grinding and polishing instruments collected in the laboratory. The energy-dispersive X-ray microanalysis used in this study helps to differentiate and delimit this form of pneumoconiosis. The pathogenesis is discussed on the basis of light and electron microscopic results and physicochemical analyses.