Ayurvedic formulations have been used for centuries with claimed safety and efficacy. The aim of the present study was to evaluate the diuretic effect of Gokshura Kwatha Marita Abhraka Bhasma (biotite calx incinerated with the decoction of Tribulus terrestris L.) in experimental animals. The animals were randomly selected and divided into three groups, each comprising 8 animals. The diuretic activity of Abhraka Bhasma (biotite calx) was evaluated by determining volume, pH and electrolyte concentration of urine in male albino rats at a single dose of 4.5 mg for 200g body weight. Furosemide was used as reference standard and normal saline was used as normal control. Abhraka Bhasma treated rats have shown significant increase in the volume of urine and urinary electrolyte concentrations of Na + , K + and Cl -ions in comparison to normal control. Thus, these results indicate that Abhraka Bhasma processed with the decoction of Tribulus terrestris L. could have potent diuretic activity.