Fibrosis involves an excess accumulation of extracellular matrix (primarily composed of collagen) and usually results in loss of function when normal tissue is replaced with scar tissue. No better example of this exists than the progressive fibrosis that accompanies all chronic renal disease. However, an overview of renal disease suggests that complementary but different mechanisms are responsible for fibrosis. Likewise, although there are obvious parallels between fibrosis in the kidney and elsewhere, there are also a number of important differences, and kidney specific consequences, that distinguish progressive renal disease. The purpose of this review is to summarise the mechanisms of renal fibrosis and its causes and consequences. In doing so it will emphasise the similarities and differences between the renal response and that of other organs.