Background and Objective: Adrenomedullin (AM) is a peptide that its production is stimulated by inflammatory processes. It is produced by different cells like smooth muscle cells, endothelial cells, epithelial cells, cardiac myocytes and oncogenic cells. In this study, we tried to evaluate the urinary AM level in children with acute pyelonephritis in comparison with healthy ones. Materials and Methods: In our case-control based study, we measured AM in 31 patients and 30 matched control by HPLC. The patients had definite pyelonephritis diagnosis based on clinical manifestations, lab data and imaging and the controls had no sign of infection and disease in their history, physical exam and lab data. For eliminating the effect of urine concentration, we compared the urinary AM to creatinine (Cr) ratio between two groups.  Results: Urinary AM to creatinine (Cr) ratio in case group was 61.3 ± 119.4 and 4.26 ± 11.4 in the control group (p=0.012). After treatment, this ratio decreased significantly to 13.1±21.9 in patients. The correlation coefficient between AM and blood WBC was 0.252 (p=0.171) that is not significant and also the correlation coefficient between AM and CRP was significantly positive, as patients with CRP < sup>+4 had a urinary AM level as 1896 ± 1748, in contrast to the patients with CRP – with a level of 391±477. This difference was significant (p=0.008). Conclusion: Urinary AM increased in pyelonephritis and it was in correlation to other inflammatory markers. It seems that urinary AM can be used as a diagnostic tool in pyelonephritis.