PURPOSE: We examined a 24-h urine to evaluate the important biochemical risk factors and relative supersaturation in patients with recurrent nephrolithiasis. METHODS: A total of 17 patients with recurrent nephrolithiasis were analyzed for urinary biochernical stone risk factors and relative supersaturation. They were evaluated using a single 24-h urine specimen with StoneRisk(R) Diagnostic Profile on a random diet. Urinary stone risk factors are calcium, oxalate, citrate, magnesium, uric acid, pH, 24-h urine volume, sodium, phosphorous. Relative supersaturation with respect to stone-forming salts such as calcium oxalate, brushite, monosodium urate and uric acid were calculated. These factors were classified one or more etiologic categories in each patient. RESULTS: Of 17 patients 16 patients (94.2%) had abnormal urinary biochemistry that placed them into one or more of 15 etiologic categories. A single abnormality was documented in only one patient. One patient had no diagnostic abnormality. High urinary sodium encountered in 13 (76.5%) of the patients. Hypercalciuria and hyperuricosuria accounted for 9 (52.9%) and 7(41.1%) of the patients, respectively. The acquired problem of low urine volume (< 2L/d) was found in 8 (47.1%) of the patients and hypoci-traturia affected in 4 (23.5%). But hypomagnesiuria was not detected. The relative supersaturation with respect to monosodium urate was highest and increased in 70.6Yo of patients. CONCLUSION: The StoneRisk(R) Diagnostic Profile using a single 24-h urine specimen is a very useful tool not only in detecting metabolic, environmental and physicochemical abnormalities but also in providing specific therapeutic or preventive guidelines of patients with recurrent nephrolithiasis. In our study the most important biochemical risk factor of recurrent stone former is a high urinary sodium. Furthermore, there is a distinct evidence of high relative supersaturation with respect to monosodium urate. High sodium intake is probably the most important risk factor in patient who develop recurrent stone formation. Therefore, dietary sodium restriction would reduce probability of recurrent nephrolithiasis.