Medicinal plants have proved to be good resource for medicines; many species of the genus Phyllanthus are used in folk remedies. In the present study aerial parts of Phyllanthus longiflorus Heyne ex Hook belonging to the family Phyllanthaceae was investigated for its possible diuretic activity. Aqueous and methanol extract of Phyllanthus longiflorus at the doses 100 mg/kg and 200 mg/kg were administered orally and the activity was ascertained by different parameters such as total urine volume, urine concentration of sodium, potassium and chloride were accounted for establishing the activity. The sodium, potassium concentrations were determined using flame photometer and the concentration of chloride was determined by titration with silver nitrate. Both the extracts exhibited a significant (P<0.01) rise in urine volume, Na+, K+ and Cl- concentration of urine in a dose dependant manner. From the findings of the present study, it was concluded that the aerial parts of Phyllanthus longiflorus possess significant diuretic activity