Nitric oxide (NO) takes an active part in the regulation of the main renal functions, water-salt metabolism, and system arterial pressure. Under pathological conditions, NO plays the leading role in the development and progression of nephrosclerosis. The aim of this study was to evaluate the clinical significance of serum and urine levels of stable NO metabolites in patients with various clinical forms of chronic glomerulonephritis (CGN), as well as CGN patients with chronic renal failure (CRF). Ninety-seven CGN patients, including 56 ones with preserved nitrogen excretion and 41 ones with CRF, were examined. The levels of stable NO metabolites (nitrites and nitrates) in serum and 24-hour urine were measured. The highest serum and urine NO levels were found in patients with nephrotic and hematuric CGN; patients suffering from latent and hypertonic CGN displayed the lowest levels. Patients with CRF had higher serum levels of NO compared with non-CRF patients. A reverse correlation between serum levels of creatinine and NO in patients with CRF was revealed. In CGN patients without CRF, the activity of inflammatory process, observed by high C-reactive protein levels, was associated with elevation of blood and urine levels of NO, while such an association was not found in patients with CRF.