There is good evidence from experimental studies that glomerular macrophages are important in acute renal injury and an increasing acceptance that they also play a role in chronic glomerular injury by stimulating mesangial cell proliferation and glomerulosclerosis. However, it is now evident that the contribution of macrophages and T cells within the interstitium must be taken into account. Indeed, if it is proved that progressive renal injury occurs via interstitial DTH mechanisms, regardless of the nature of the initial glomerular insult, then such mechanisms may provide a suitable target for the development of novel therapeutic strategies.