Pneumonoconiosis includes all forms of pulmonary fibrosis occurring as a result of the inhalation of organic or inorganic dust. It is definitely an occupational disease and is rare outside of large industrial and mining districts. The group comprises: Anthracosis—inhalation of coal dust. Siderosis—inhalation of iron and steel dust (usually by metal grinders and polishers, nail and file makers, and so on). Chalicosis or silicosis—inhalation of stone dust (usually by stone workers, such as potters, grinders, plasterers, porcelain makers or quarry workers). This report is concerned with chalicosis or silicosis. Under normal conditions the lung is fairly well protected from ordinary amounts of city dust. This protection is effected by the action of the ciliated epithelium, phagocytes, mucous secretions, and the cells of the bronchial tubes. However, in persons who work in atmospheres heavily laden with dust these protective mechanisms are insufficient and depositions of the particles occur.