Primary nocturnal enuresis (PNE) is the most common type of nocturnal enuresis in children, but its etiology remains unclear. Recent studies indicated the differences in urinary electrolytes in enuretic children, and stressed the existence of a renal tubular maturation defect. In this study, 30 children (aged 6-12 years) with PNE were investigated in comparison with 18 healthy controls. We evaluated plasma antidiuretic hormone, electrolytes, 24-h urine volume, osmolarity, and urinary electrolytes. Unlike other studies, we firstly assessed the plasma and urinary adrenomedullin (AM) and total nitrite levels, a stable product of nitric oxide (NO), and investigated their relationship with urinary electrolytes. The plasma AM and total nitrite levels were significantly lower than controls. Urine volume (24-h) and potassium excretion were higher than in controls. However, 24-h urinary osmolarity and excretion of AM were significantly lower than in controls. Our results indicate that there may be a problem in renal regulation of potassium in children with PNE. Although decreased levels of AM and total nitrite may be a compensatory response to abnormal potassium and water excretion, further investigations are required to exclude whether the renal synthesis of AM and NO are also deficient in these children.