In 30 patients with silicosis, some abnormalities of static lung volumes and mechanics of breathing were found despite normal spirographic performance. Although FEVi.o/VC was within normal limits, several subjects had hyperinflation and an increase in difference between static and dynamic lung compliance. The static lung compliance showed a wide scatter; however, seven patients (three from among the five patients with advanced silicosis) had a compliance under the lower normal limit, while a further four had “borderline” low values. In interpreting the physiologic abnormalities of the lung in patients with silicosis, the influence of age and smoking habits must be taken into acount.