Six cases of silicosis were autopsied and the postmortem changes were compared with clinical manifestations. Gross and microscopic findings of pneumosilicosis were described and three distinct morbid morphological units, namely, early silicotic nongranulomatous changes, silicotic granulomatous changes, silicotic granulomatous nodules and conglomerated silicotic nodular masses, were presented. These three changes proceded in the order successively in progress and in parallel. However, the last change was self-limited within the lobar dimension. The details, of each unit were as follows: Early silicotic non-granulomatous changes. The earliest chief finding was the accumulation of dust cells laden with silica in the alveolar spaces and in the alveolar walls. The next stage finding of the earliest change was composed of many foci with silica laden macrophages and the nearby fibroblasts proliferation around the small vessels and bronchioles. Silicotic granulomatous nodules. The nodules consisted of centrally located layers of concentric hyalinized collagenous tissue lacking macrophages and anthracotic pigments. In the peripheral area of this nodule. many macrorhages laden with anttracotic pigments and silica and proliferation of fibrotlasts inter-mingled with anthracotic pigments were found. Conglomerated silicotic nodular masses. Grossly many nodules, 1∼5mm in size, were conglomerated into a large compact mass occupying almost the entire lobe. The main changes appeared chiefly in the apex of the lung and near the hilum. Fibrous tissue between the nodules showed no concentric arrangement and became partially hyalinized. Combined changes were as follows: bronchitis, bronchiectasis, tuberculosis, lobar pneumonia, emphysema and congestion and edema. Among these changes, lobar pneumonia, marked congestion and edema and corpulmonale seemed to be lethal complications.