The term pneumonoconiosis has been so loosely applied to industrial pulmonary conditions that some clarification appears to be desirable. It is an allinclusive caption for a variety of pulmonary affections resulting from the inhalation of inert or harmful dust. Generically it does not imply fibrosis but simply "dust in the lungs." If one is to accept this meaning, therefore, pneumonoconiosis must include any retention of dust in the lungs, whether of industrial origin or not and whether of toxic, irritant, proliferative or inert dust. It must also include the anthracotic pigmentation from dust, carbon and smoke which all normal lungs exhibit; in the interpretation of pathologic change, the matter of degree as well as specificity must be considered. From a practical standpoint, however, pneumonoconiosis refers mainly to pulmonary alterations attributable to those dusts encountered in industry which can cause proliferative reactions, roentgenologic patterns due to radiopaque properties or simple exaggeration