Aim: Adrenomedullin (AM), a novel peptide recently isolated from pheochromocytoma, eliciting vasorelaxing activity, is the strongest among all known peptides. AM has been detected in the adrenal medulla, cardiac tissue, lung and kidney. Immunohistochemical studies have demonstrated the localization of AM in glomeruli, tubules and collecting cells of the kidney. Clinically, plasma and urinary AM levels are altered in patients with different renal disease. The present study aims to determine plasma and urinary AM levels in children with acute pyelonephritis (APN) and compare the results with a control group.