Fibrocytes are bone marrow-derived, circulating mesenchymal progenitor cells that play a role in several fibrotic disorders, including lung fibrosis. They are attracted to injured tissue by various chemokines. It is likely that fibrocytes play a detrimental role in tissue homeostasis and promote fibrosis, although this paradigm needs further confirmation. This would make fibrocytes a possible novel treatment target for fibrotic disorders. Fibrocytes also have some potential as a biomarker for idiopathic pulmonary fibrosis (IPF) and other diseases, but the promising preliminary data from single centre studies still require independent validation. Despite several, as yet, unresolved issues, it has become clear that fibrocytes are more than an incidental finding in lung injury and repair, and may hold great promise for the future of IPF management.