Seeds of Macrotyloma uniflorum Linn. (Fabaceae) are widely used for treatment in kidney stones in India. In This study evaluates the invitro effect of methanolic extract of Macrotyloma uniflorum (MEMU) on calcium oxalate crystallization. A methanolic extract of M. uniflorum seeds at different concentrations (250-1500 μg/ml) was subjected to in-vitro crystallization activity. The obtained results were compared with a Cystone (standard herbal product) available in the market. The nucleation and crystal growth assay was performed with different concentrations of sodium oxalate (2-10 mmol/ml for nucleation, 2-3.5 mmol/ml for crystal growth) and evaluated the effect of MEMU and cystone at different doses (250-1500 μg/ml) on the different concentration level of oxalate. Crystal aggregation and crystal dissolution assay were performed and compared with cystone effect. The MEMU was significantly more effective than cystone at inhibiting the nucleation rate and crystal growth at a different concentration level of oxalate. Inhibition of calcium oxalate crystal aggregation and dissolution was observed in a dose-dependent manner. The results showed that MEMU has excellent in-vitro calcium oxalate crystallization inhibition activity in the different concentration level of oxalate and also have crystal dissolution activity; therefore, it might be useful in the prevention of renal stones.INTRODUCTION: Kidney stones are the solid crystalline masses that occur anywhere in the urinary system, and it is often correlated with habits such as high purine intakes, obesity, hypertension, metabolic syndrome, and diabetes 1 . A large number of people, nearly 4-15% of the human population, suffer from the renal stone problem all over the global 2 .