currently it has got various other applications in Anaesthesia. The ideal osmotic agent should establish a strong trans- endothelial gradient by remaining in intravascular compartment. It should be inert, non-toxic and should have minimal side effects. Various substances that have been used and investigated are Urea, Glycerol, Mannitol and Hypertonic saline. Urea has serious side effects. Glycerol is moderately successful in decreasing intracranial pressure and may cause hyperglycemia .Mannitol is safe and effective. The limitations of mannitol are increase in hyperosmolality.> 320 mosml/kg.