OBJECTIVE: To measure peripheral serum levels of matrix metalloproteinase 9 (MMP9) and matrix metalloproteinase 19 (MMP19) in patients with pneumoconiosis, and to investigate their feasibility as potential biomarkers for pneumoconiosis. METHODS: Ninety-eight male patients with pneumoconiosis (49 patients in phase I, 36 patients in phase II, and 13 patients in phase III) were enrolled as subjects, which included 41 patients with silicosis and 57 patients with coal workers' pneumoconiosis. Ninety-eight healthy male physical examinees were used as controls. A fasting blood sample (3 ml) was collected from the peripheral venous blood of each patient or control, and the serum was separated from the blood sample. The expression levels of MMP9 and MMP19 in serum were measured by enzyme-linked immunosorbent assay. RESULTS: Serum levels of MMP9 and MMP19 in patients with silicosis or coal workers' pneumoconiosis were significantly lower than those in the control group (P < 0.05). Serum levels of MMP19 in patients with silicosis were significantly higher than those in patients with coal workers' pneumoconiosis (P < 0.05). Serum levels of MMP19 in patients exposed to dust for less than 7 years were significantly higher than those in patients exposed to dust for more than 20 years (P < 0.05). There were no significant differences in serum levels of MMP9 and MMP19 between patients with different levels of pulmonary function impairment (P > 0.05). Serum expression levels of MMP9 and MMP19 were positively correlated with each other in both patients with pneumoconiosis and those in the control group (P < 0.05). The serum expression level of MMP9 was negatively correlated with the stage of pneumoconiosis (P < 0.05). CONCLUSION: Serum MMP9 and MMP19 may be used as potential biomarkers for pneumoconiosis.