The shade-dried powder of leaves of Plectranthus amboinicus (Lour) Spreng was subjected to successive extraction using the various solvents (petroleum ether, chloroform, ethanol and water) in increasing order of polarity. The preliminary phytochemical analyses were carried out for all the extracts. The analyses of the leaves revealed the presence of alkaloids, carbohydrates, glycosides, proteins, amino acids, flavonoids, quinine, tannins, phenolic compounds and terpenoids. Since the phytoconstituents present in the ethanolic and aqueous extracts were similar, both the extracts were selected for further study. The diuretic properties of ethanolic and aqueous extracts were evaluated by determination of urine volume and electrolyte concentration in male albino rats. Furosemide (10 mg/kg) was used as standard while normal saline (0.9%) was used as control. Both ethanolic and aqueous extracts (500 mg/kg) have shown significant increase in the volume of urine and urinary concentration of Na, K and Cl ions. Thus, from the is study it may be concluded that the leaves of P. amboinicus (Lour) Spreng possess diuretic activities.