The present series comprises 2086 consecutive patients who were studied in a stone clinic during a period of 15 years. Each patient was subjected to a comprehensive protocol including a fully biochemical investigation. Calcium stones were by far the commonest accounting for 61% of cases; infection, uric acid/calcium oxalate and cystine stones accounted respectively for 24%, 8%, 5% and 2%. Nephrolithiasis was more prevalent in males with the male to female ratio 1:0.76, on the other hand infection stones were more frequent in females with the male to female ratio 1:1.6. The peak age incidence of renal calcium stones occurred in the third to fifth decades, although about 3.4% reported onset of disease in the first and second decades of life. The onset of cystine stones was always in the first and second decades, while uric acid stones affected older patients. Renal stones were recurrent in about 50% of cases. In a retrospective analysis it was found the interval to first recurrence to be less than 5 years in about half patients. The cystine and uric acid groups had the highest rate of recurrence. In patients with calcium stones a definite metabolic or mechanical cause for their stones was found respectively in 8.2% and 10.1%. Particularly primary hyperparathyroidism was revealed in 2.8%. A metabolic defect could be found in 54% of the patients with idiopathic calcium stones. In these patients with idiopathic calcium stones the prevalence rate of hypercalciuria was 33%. In patients with uric acid stones and with mixed uric acid/calcium oxalate stones a definite metabolic cause for their stones was found respectively in 9.5% and 4.1% whereas an underlying disease of the urinary tract was diagnosed respectively in 8.5% and 6.2%. In patients with struvite stones the incidence of persistent infection was 46% (Proteus 18%). In this group the presence of an underlying disease of the urinary tract was diagnosed in 18.8% whereas a definite metabolic disease was demonstrated in 8.5%, a urinary risk factor for metabolic stone disease in 42% and a previous episode of metabolic stone disease in 33%.