To determine whether expression of the renin-angiotensin system (RAS) is influenced by the degree of renal ablation, male Sprague-Dawley rats underwent uninephrectomy, 1 1/3 nephrectomy, or sham operation. Renin and angiotensinogen messenger RNA (mRNA) were not different among the three groups 2 weeks after surgery. The time course of expression of renin mRNA after 1 1/3 nephrectomy showed no difference versus controls at 2 and 4 weeks and a decrease at 6 weeks after surgical ablation. Because nephrons adjacent to the infarcted area in the 1 1/3 nephrectomy may be hypoperfused and a source of increased renin synthesis, intrarenal distribution of tissue renin content, renin mRNA, and immunostainable renin were examined in separate groups of rats subjected to 1 1/3 nephrectomy. The kidney was divided into two pieces, one containing the scar and scar-adjacent tissue and the other portion the tissue distant from the scar. Tissue renin content, renin mRNA, and immunostainable renin were significantly greater in the scar-adjacent tissue compared with the nonscar tissue. Immunoreactive renin was seen in the juxtaglomerular apparatuses as well as in vascular elements proximal to the juxtaglomerular apparatus and within mesangial cells of some glomeruli of the scar-adjacent tissue. In conclusion, immunostainable renin, tissue renin content, and renin mRNA were increased in scar-adjacent tissue after 1 1/3 nephrectomy. We speculate that this unique scar-associated redistribution of renin may play a pathophysiological role in the progression of renal disease.