Chloride is the most abundant anion in the extracellular fluid. It ensures appropriated osmotic pressure, hydrous distribution and anion-cation balance. Its concentration is similar to that of sodium and is influenced by the same factors. Determination of plasma CI, concentration is useful in the differential diagnoses of acid-base disturbance and is essential for calculation of the anion gap measure in urine is of clinical value with patients with persistence metabolic alkalosis who are not receiving diuretics. Hypochloremia is observed in individuals with salt-losing nephritis coupled with hyponatremia and in case such as bromide intoxication, SIADH expansion of extracellular fluid, metabolic acidosis or persistent gastric secretion and prolonged vomiting. Hyperchlormia accompanies dehydration, RTA acute rena failure, metabolic acidosis , diabetes insipidus, extremely high intake of slat.