Serum total sialic acid and C-reactive protein (CRP) were studied in 68 patients with silicosis divided into 3 groups according to the evolutive stage of disease. The results were compared with the data obtained in a control group of 35 healthy subjects. The changes in serum total sialic acid levels were in parallel with those of CRP in silicosis. Patients in stage III had the highest mean values of serum total sialic acid (p < 0.01) and of CRP (p < 0.001). Linear regression analysis revealed a close positive correlation between serum total sialic acid and CRP levels in silicosis (r = 0.86, p < 0.01).