Macrophages evolved to maintain and restore tissue integrity. They originate from bone marrow-derived precursors and traffic through tissues where they have essential roles in remodelling during fetal development; in host defence against infection and tumours; and in wound healing . Macrophages also mediate injury in immune-mediated diseases including glomerulonephritis, and this aspect of their function together with their role in combating infection have tended to overshadow their involvement in tissue repair. Understanding how macrophage function adapts to the needs of particular microenvironments is a principal challenge for inflammatory cell biologists. Importantly, learning to manipulate macrophage function to promote their reparative properties would be a powerful therapeutic tool, a point emphasized by the recognition that many viruses, parasites and tumour cells have evolved to redirect macrophage function to promote their survival . Our purpose here is to review briefly what is known about the role of macrophages in renal injury; to describe recent advances in understanding of macrophage activation; and to show that manipulation of macrophage function can have profound effects on the intensity of glomerular inflammation.