Experimental model of 5/6 nephrectomy or the remnant kidney model represents one of the most used animal models of progressive renal failure by reduced nephron number, best-characterized in rats. The reduction of renal mass is achieved by either infarction or surgical excision of both poles, with removal of the contralateral kidney. It enables to investigate the influence of pharmacological, nutritive and other factors on functional and morphological renal parameters. 5/6 nephrectomy produced by infarction is characterised by high plasma renin levels. By contrast, reduction of an equivalent amount of renal parenchyma by surgical excision does not result in the development of hypertension and plasma renin activity is normal to low. The initially normal remnant nephrons undergo compensatory functional and structural adaptations. Simultaneous glomerular hypertension is one of the main factors responsible for the development of renal injury. Morphologicaly progressive focal segmental to global glomerulosclerosis is present, accompanied clinically by increasing proteinuria and deteriorating renal function.