Fibrocytes are bone-marrow derived mesenchymal progenitor cells. They express typical markers of leukocytes, hematopoietic stem cells and fibroblasts. They play a pivotal role in the tissue remodeling and fibrosis in both physiologic and pathologic settings. Fibrocytes are unique in that they are capable of differentiating into fibroblasts and myofibroblasts, as well as adipocytes. Circulating fibrocytes may play a role in pulmonary fibrosis and clinical outcomes. Recent data obtained from the clinical setting suggest that high numbers of circulating fibrocytes correlate with pulmonary function test parameters and disease activity in patients with different interstitial lung diseases. A greater understanding of the immunologic mediator that influence fibrocyte biology suggest new opportunities for therapeutic manipulation of these cells in fibrogenesis.