Citrate is a tricarboxylic acid, synthesized in mitochondria from oxaloacatate and acetyl CoA by the enzyme citrate synthase.1, 2 Citrate is thought to be freely filterable at the glomerulurs, in humans, 65 to 90% of the filtered citrate is reabsorbed and 10 to 35% is excreted in the urine as a byproduct of oxidative pathways in the body.3, 4 It is known to inhibit precipitation of calcium oxalate and phosphate and growth of their crystals5 . In 1990 Pak has defined normal 24 hour urinary citrates as more than 320 mg for both genders6 . Hypocitraturia is defined as urinary citrate excretion lower than 1.67 mmol (320mg) per day. However, there are some reports of low urinary citrate output in stone formers (SF) and renal failure as compared with healthy subjects7-9 , while other studies found no differences10,11