Renal tubules and interstitium have close physiological associations. Changes in both are often seen in renal disease. Damaged tubules can attract inflammatory cells and stimulate interstitial fibrosis, but do not always do so. Interstitial inflammation can damage tubules and can also stimulate fibrosis, and is probably always initiated by tubular events. Interstitial and tubular abnormalities are closely associated with changes in renal excretory function, but tubular events are more important. A main determinant of the outcome of renal disease is whether tubules can recover, not the extent of interstitial changes. If tubules are atrophic, they will not recover and renal function will be permanently impaired.